i suspect that spanish has japanese beat in this regard because of its relatively larger geographical dissemination makes formality based grammar rules incompatible with each other -- effectively making all incompatible versions technically correct despite literally contradicting each other.

it's one of the reasons why a majority of non-spanish speakers are taught european spanish rather than any of the SIGNIFICANTLY larger versions of spanish that exist.

japanese formality system is not that hard, it's a couple conjugations and it pretty much doesn't change when it comes to gender, singular/plural, etc. it's really exaggerated how difficult that is. spanish doesn't have that many grammar rules for formality in that sense, but it adds another personal pronoun just for that.

also counters is also something shared among all languages pretty much. a school of fish? sure... it's just whatever word/ideogram the language speakers decided it was what's best to describe that group.

i'm not saying japanese is easy, just that some of those things are a bit not so much an issue as people make it seem to be. i am a native spanish speaker and i have practiced japanese for some time so i know a thing or two about that.

Spanish is more inflectional than Japanese. Keigo, the more respectful forms, holds cultural nuance, yes; but it isn't standardly required for meaning.

Japanese is the more foreign language, but I've felt fairly let-off-the-hook as far as inflection goes.