This is not just grammatical history, this is the current grammar rules.
However some people are trying to force a change of the rule by making up new words and rules, such as "iels" instead of "ils/elles".
What I am missing are the concepts young people are bringing in more and more, where they have words that become unisex (potes for instance). I listen to my children and (without any scientific analysis), it sounds to me that there is less of a boy/girl cut that there was in my times (this may be regional - this is for west of Paris).
And I agree with you that only naturally appearing changes will stay, not the ones forced on us. A typical example are the surrealist ideas of the 90's to have French equivalents for everything computer. Some stayed, the majority is now part of comedies.
If you follow the grammatical history of French, the neutral gender just got folded into masculine.
>but some innovative-but-not-distruptive changes would be welcome
You can't really produce grammar by decree, at best you can systematize what already exists. The only "sane" way to have explicit neutral in French would be to go back in time, reimplement declensions and possibly mangle phonology in the process. That won't happen. All forms of "inclusive writing" are from the outset destined and meant to be an elitist signal rather than an actual linguistic feature. They won't survive and they'll been seen in the future as a strange, idiosyncratic trend of the age. A bit like Renaissance orthography, where countless letters were added without meaning to simply look fancier.