I think a lot of people forget this applies to Hellenic Polytheism / Greek religion and spirituality as well!
A lot of neo-pagans and new ageists completely sweep traditional & modern Greek practitioners under the rug, and it has resulted in a lot of people trying to force "HelPols" into a monolith. In reality, there was always MANY ways to practice and still is, because every Greek region, kingdom, polis, household, was different.
It's really unfortunate because they're both attacking actual Greek practitioners practicing our very much alive religion, as well as beginners trying to learn who may do things differently than others.
Diversity in Greek culture has always been relevant and beautiful, and that applies to religion and spirituality as well.
First and foremost, modern and living examples - you can find people online (I have a guide to conducting research and verifying the credibility of people / sources here), but I am one of them too! I LOVE answering questions so feel free to send an Ask if you have any! Please note that many traditional practitioners won't speak to you because of how oppressed we're becoming in the HelPol community, but there are some if you have good reasons for learning (i.e. not just trends)!
For me, I practice very traditionally, but I'm also Biracial so there's a mix. I would say when it comes to the Greek side of things, I follow some less popular beliefs. Some are less popular due to neo-pagans, and some are less popular among other traditional Greeks. For example, I'm an Energy Force Practitioner, which is traditional in Greek (and other) culture(s) but not inherently super popular. Another example, I believe the gods aren't gods but rather just "high status" spirits - again, traditional, but not the most popular. Again, there is no monolith, so these things are what resonates with me and my teachings and my cultural path as a Greek / Mixed person.
Some other random beliefs I hold: you can work with the gods (this is a popular one for many traditional Greek practitioners actually!) rather than worshipping them (Greek religion is traditionally transactional, after all), good company is a perfectly fine offering (offerings do not need to be material and it's perfectly fine to be "friends" with gods because they are individuals just like we are, we can be strictly business but we do not have to be), gods and humans are equal beings (one is not better than the other, just different), we should be ASKING the gods things rather than assuming as they are autonomous and it's important to listen to them when we ask for answers (it's disrespectful otherwise), the deities aren't perfect and have dark sides, the myths and lore are not often literal, deities can hear our thoughts and their names still have power, tricksters and harmful spirits exist AND can pretend to be gods whether on purpose or to the fault of the practitioner (I actually have a post listing a shitload of harmful spirits as proof), vetting is important and so are protections (also very common with traditional Greek practitioners, a few of these have been common ngl), and so on! Most of these are traditionally Greek concepts!
Ever wonder why some cities had temples for some gods but not all? This is why! Because some regions, cities, etc, had varying beliefs on the gods - sometimes they emphasized different gods and didn't worship others, sometimes they had different ideas and teachings on that specific god, etc!
Athens is known for admiring and honoring Athena
Thrace is known for admiring and honoring Ares (the only Greek city to have temples for Ares btw)
Aphrodite is known to be worshipped in Cyprus, as well as about 3-5 cities if I recall correctly
And it goes even deeper. Some households or areas would focus on different epithets, different reasons to call the gods, etc!
Why did / does every Greek household have different beliefs as well?
This is a broad question as every region / polis / etc was different and every individual is different, but there's two main reasons I'd like to hone in on.
Firstly, personal preference. It truly is that simple. Religion and spirituality are incredibly intimate, so it has always been natural to have your own ideas or variations on things, based on what resonates with you or your personal experience with the gods. This has always been the case traditionally (at least in a good portion of Greek areas / communities), which is why things like "UPG" doesn't always necessarily apply to Greek religion and spirituality.
Secondly, personal needs. You know how sometimes you just don't really vibe with a god, or don't really need their support with anything for a while? Literally, the ancients were just like that too, and many of us traditional practitioners are still like that today! If you weren't by the sea, you may have not needed Poseidon or Amphitrite every day. If you focused on working with plants, you probably weren't going to Hekate on the daily for that. If you needed support with music and arts, you likely called on the Muses. If you were working consistently with Hera and were in an emergency, you likely called on her before another god. The point in polytheism is that one god cannot and does not do all things (that's why there are multiple gods), so why would we expect humans, past or present, to do all things?
Additional to the "personal needs" aspect, this goes beyond just work / worship and into lore as well! Many of us had our own variations of the myths and stories (oral traditions) passed down depending on our life, our kids and the people in our life, the regions we were in, etc! For example, that's why the kidnapping of Persephone sometimes describes her as an adult and sometimes as a child. IIRC this was actually originally a Roman myth (which I'll talk about Rome next), but in Greek aspects, think about it like this: If you're speaking to a woman who doesn't have and likely won't have kids, the story of a woman losing her child is something she can be empathetic for but still not much she can learn from. The myth is told to explain how death does not discriminate, so changing Persephone to an adult - such as her niece who's now a teen or helping her reminisce of her early days - would have a greater emotional impact. Of course, this is just a brief example off the top of my head, there's nuances and other examples, but you get the point I'm trying to make.
Rome - and why this matters in this conversation?
Many neo-pagans conflate Greek Polytheism and Roman Polytheism in a very unfortunate way. Even during syncretization of the two, there were notable differences, and the eras before and after that time did not involve as heavy of syncretization. I am not saying being a syncretist is bad, but this is something not a lot of people know.
Romans had their own culture - and their own gods - before they even syncretized with the Greeks later or adopted Greek gods (and other gods, as Romans were traditionally Omnist). Romans were technically a branch from Greece as their own city - so, they were a Greek culture originally that became their own (Roman) culture when they built Rome. I'm highlighting this because it is a grand example of how Greek regions, kingdoms, cities, etc, could be so vastly different that they forged an entirely new belief system and culture and branched off of us. This alone truly signifies how disgraceful and disrespectful it is to try to force our teachings into a monolith.
Just adding onto this, there are many other examples of this. Each city having different beliefs, but also various cultures - Greeks, Romans, Persians, Turkish, etc - mingling and mixing beliefs (that's how we got Dionysus)! For Greeks, there was a lot more syncretism, but it usually manifested in adopting just a different version of that deity (again, that's how we got Dionysus, and a few others as well - possibly Cybele, who is syncretized with Rhea)!
It is important to recognize the diversity of any culture and remember that seeing us as primitive is rooted in colonialism and forced conversion into Abrahamic religions (Christianity, mainly). We were not so "simple," and even if we were, I'd like to highlight again: There are MODERN Greek practitioners. The religion is not dead. We just keep things much more private now due to the harm both Christians and neo-pagans have done - and still do - to our community. Just as any religion, culture, community, people, or belief system, has grown, innovated, developed, and evolved over the years, so have we. Please, if you're gonna call yourself a HelPol, shed some respect on our name!
Thank you so much for reading! Please feel free to send an Ask with any followup questions or random things you'd like my thoughts on! And, check out my pinned post / table of contents to learn more about the information I post. Thanks! <3