it's fascinating to me how endlessly complicated High Valyrian seems to be when you answer questions about it. Is there any language in the world more or less at the same level of complexity?
It depends how you're thinking of complexity. All the languages of the world are equally complex. They have to be, because they all need to perform the same function, and they're all used by the same human brains living inside the same humans living human lives. I think English speakers (and hypothesize that, by extension, the same would be true of Chinese speakers, Hawaiian speakers, Vietnamese speakers, Swedish speakers) look at certain other languages and think of as more complex in the meta sense because they are more morphologically complex.
By this, I mean in English, for a noun you need to know its singular and plural form—that's it. For a verb, you need to know its -s form, its -ed form, its -ing form, and, very rarely, its -en form. There is some irregularity in form for almost all of these (-ing appears to always be regular), but there aren't more forms, outside of "to be", which has a unique first person singular form.
And...that's it, really. We have adjectival comparison, I guess, but even that can be traded out for an expression (aside from "better" which can't be replaced easily by "more good", most comparatives can be replaced—e.g. you can say something is "more red" than something else even though you can also say it's "redder" than something else). There aren't many word form changes in English a user has to learn in order to be able to use those words in a sentence. The same is true of those languages I listed in the parenthetical phrase above.
Compare that to Spanish, where there are more word form changes for verbs in the present tense (indicative and subjunctive) than in the entirety of English. And that's just one tense for verbs! There's loads more that needs to be memorized; many more word form changes you need to know to be able to use words effectively in a sentence. And there are irregularities on top of that!
Is it the case, therefore, that Spanish is more complex than English?
Certainly, Spanish is more morphologically complex, but does that mean you can express more in Spanish than you can in English? Certainly not! So then what does it mean when we say Spanish is more morphologically complex than English? What's the upshot? What does it mean for the language user?
Perhaps it would help if we compare some Spanish verbs and their English translations:
hablabas "you were talking"
The precise translation of these verbs will depend on context, but this is a fine example. These are all single words of Spanish. They're different forms that must be memorized, but they're single words. The English requires at least two words for each concept.
So which is more complex? On the one hand, you have fewer words but more forms. On the other, more words, and more words = bigger.
And that, essentially, is the crux of it.
Any time you have complexity baked into single words morphologically in one language, you'll find complexity in the form of multiword expressions in a less morphologically complex language. The meanings are always there(*), but they're expressed in different ways.
As English speakers, we're used to having to express things in multiword expressions, and a speaker of a given language will find their own language to be simple just because. We extend that to think of languages like ours as simpler than those that are different. But, in truth, it's six of one, half dozen of another. Furthermore, there's just as much complexity in languages with less morphological complexity. Consider the following expressions in American English:
That's pretty standard. English has articles and you need to use them, right?
All those are okay. They don't mean the same thing—and, indeed, the first two have much more restricted contexts—but they're all okay. That's a little weird, isn't it?
The first two aren't just weird: they're yikes-a-doodle-do wrong. You might try to brush it aside and say that it's just an expression, and, sure, it is, but ask yourself this: how'd that expression come about in the first place? This one is actually from Shakespeare (Romeo and Juliet) and still works the same way in American English:
You might think the way these shake has to do with what they stand for—that the semantics of the noun in question condition whether or not you can use articles—but consider the first one "store" and compare it to this one:
I walked to the Barnes & Noble. ✅
I walked to a Barnes & Noble. ✅
I walked to Barnes & Noble. ✅
Barnes & Noble is a store, but refer to it by title, and suddenly it's all okay.
Now, if your native language is English, ask yourself: when and how did you learn all of this? Did someone sit you down and tell you where to use which articles and where not to? I'm sure there was some level of instruction you got in elementary school (whether it was accurate or not), but how much of a difference do you think that made? Did you just not use articles before then? And even now, could you explain this? Do you even think about it? Or do you just do it—flawlelssly and effortlessly? Adult learners of English will tell you learning this stuff is a nightmare. Throw in phrasal verbs (pick up vs. pick out vs. pick on vs. pick up on vs. plain old pick) and suddenly English doesn't look too simple anymore.
Bringing this back to your question, when you look at High Valyrian, is there a natural language with an equal amount of morphological complexity? Sure. Maybe something like Latin. But understand that any language will be as complex—not more, not less: as. The only difference with High Valyrian, actually, is its vocabulary isn't as large (give me a couple decades), and it doesn't have nearly as many users as any natural languages. It's also being kept artificially small, in that the language is built up to fit a fictional reality, rather than being expanded to handle anything, the way modern languages are. But pick up any language and it will be equally complex.
(*) From above, it is not always the case that the same "meanings" will be in the equivalent translation of a given sentence. A good example is gender. If you say El río es largo in Spanish it means "The river is long" in English. Like, exactly that. There is no question that these two phrases are functionally equivalent. HOWEVER there is more information in the Spanish sentence. The words el, río and largo are all masculine gender. What does that mean? Nothing more than that they're not feminine. If you hear el in Spanish there are a limited number of words that can legally follow it. When you hear largo, you know that what it refers to has to be in the same class. The function of this is simply to enrich the signal. If you only hear "is large" in English from the previous sentence, you have no idea what noun is large. If you hear es largo in Spanish, you also don't know—but whatever that thing is, you know it has to be masculine. That means that if a Spanish speaker has to guess what es largo they were trivially have a better shot at guessing correctly than an English speaker guessing what "is large" (e.g. if an English speaker has a one in a million shot, a Spanish speaker has a one in 500,000 shot, because roughly half the nouns of Spanish are masculine and half feminine). This means, technically, there's more information in the Spanish sentence than the English sentence, and that information is not represented at all in the English sentence, and is, essentially, unrecoverable. But that "information" is more morphological in nature than semantic.
