Are you sure you are actually understanding the subtleties? I can definitely read latin and work out what is meant. But when I read my native languages, I can tell that there's A LOT of meaning hidden in subtleties that I would definitely lose if I were to analyze sentences only through etymological meaning of each independent word, to say nothing of the pain of having to parse ambigueties:

e.g:

Ambigueties: "Defended Warrior" - "Warrior Defends" / "Bellator defendit" - "Bellator defensus"

Subtleties: - "Defense! Defense!" "Defend! Defend!" (Basketball vs war)

- "No good", bad? Or bad/neutral?

- "Do you take me for a fool" / "Do you think I'm dumb?" (Accusation of cheating vs Earnest)

That's not to say you don't have the tools to derive meaning from context and parse ambigueties, but if you are simultaneously parsing syntactic ambigueties, then you have much less energies to parse semantic ambigueties and to try to work out what idiomatic phrases would have meant.

And the effect is multiplicative, if you have 2 declensions you don't remember, you have 4 combinations to parse. Multiply that by 2 possible meanings of the phrase (or more) and you have 8 meanings ( or more).

Sure, you can read somewhat, but I'd be skeptical as to how much you can understand what you are reading, sure it's more than chinese since we share a lot of roots, but there's still a lot of meaning that is missed, and knowing declensions is like level 1, it doesn't guarantee you will understand latin either.

Right, and we descend from amphibians, but we diverged quite a lot.

I took a look into german, it seems that their case system is much more stable than latin, based on suffixes mostly, and most words having the same form for many cases.

Why genders or specific declensions exist? Being a native spanish speaker I can say:

- Error correcting code: If a gender or number doesn't match, you can reparse what you heard, or ask for clarification.

- Proof of consistent thought: Forces to think ahead in sentences, you can't just make things up as you go, if you used an article early in a sentence it's because you already know what you are referring to. If someone can't even match their genders or numbers, you can pretty much discard what they are saying, or surmise they are intoxicated. Consider how basic autopredict would fail and instantly be detected in spanish, while not necessarily so in english.

As for latin declensions: - Classism: I don't think the purpose of language is always to increase communication, I think that a high bar for communicating was placed, no doubt there existed simpler languages that could have reached more penetration, but I believe that the incredible amount of cases serves as a test of memorization, a display of mental virtue which one must pass through in order to be worthy of communicating. It would not doubt be a more extreme form of proof of consistent thought, but I imagine it would be much more notable, it would be easy for a roman citizen to detect a non citizen or a slave by how they talk based on their lack of schooling, maybe they couldn't even form complete sentences to collude, they could just be limited to saying yes/no.