“Fish” and “fishes” already have distinct meanings, IME and O. The former may indeed refer to one or many individuals, or to their flesh, but the latter means a catalog of many kinds.
Some of us like the fact that our language is so rich and varied, with so many idiosyncrasies. I personally consider that a beauty in and of itself, and it turns mastery of the word into an art, not a science. I’d be very sad to see everything standardised and turned into something akin to a computing language.
This in itself is a little insanity. The actual phrase is: “What’s sauce for the goose is sauce for the gander” or substitute “good”. Not plural goosen.
It’s precisely because language has a natural drift that propositions like this (aiming to impose a simple orthodoxy on language) are misguided and futile.
The benefit would be marginal at best - even children can deftly integrate the caprices of our conventions regarding spelling, grammar, and modification of words. It’s not that hard, and not really a problem that wants a solution.
Because the drift is gradual, our written legacy is accessible without too much difficulty. If we reduced things to the simplest of rules and turned our back on that, it would make this legacy much less accessible to new generations who have not learned these conventions organically, so the cost would be high - and then, because language is language, it would continue to drift anyway. It’s like Xerxes trying to discipline the sea.