So I'm rocking up late to the party having finally started watching FROM and, admittedly I do have some spoilers from season four because I was in the room when my stepdad was watching some episodes and I'd like to weigh in with my five cents about the Jim hate.
At first I didn't get it, but now that I'm on season two I do understand the Jim hate, his we're in a simulation no I will not listen to any other explanation / evidence about this thank you very much is COMPLETELY insufferable.
BUT, I will say, based on season 4 spoilers, I don't know that was entirely Jim's fault. Based on what we've seen of the entities (particularly the Man in Yellow, but Boyd had moments of buying into the dream theory after being bitten by the spiders/infected by worms) they make you doubt your reality. The Girl in Yellow was making Henry believe he was in a coma, we don't see if anything proceeds the Abby believing they're in a nightmare rampage, but my personal headcanon is that an encounter with an entity may be proceeded it, possibly even the MIY in one of his other forms.
And what happened before Jim suddenly came up with this theory? He spoke to the Man in Yellow on the radio.