The question is whether a commitment continues to bind a community even after several generations have already abandoned it. For example, suppose some community within the Jewish people committed itself to follow a certain halakhic decisor, and at some point most members of the community adopted a different decisor instead (this is apparently what happened among Yemenite Jews, some of whom moved from Maimonides to the Shulchan Arukh). Are they obligated to go back and all follow the first decisor?

In simple terms, yes, but in any case that is not the situation here.
Beyond that, adopting a halakhic decisor is not a commitment but a custom, or at most a vow. A commitment is toward someone (a contract). And a contract remains binding even if people negligently abandoned it midway.

Does communal acceptance mean that the Holy One, blessed be He, obligates every Jew to act in accordance with the acceptance of his ancestors, and that this acceptance is the condition that gives rise to the commandment, like the commandment of first-fruits for someone who has produce? Or is it an independent reasoning, like the logic of civil law? Truthfully, I’m not sure that in your approach there is a sharp difference between the two (though still, as an independent reasoning, communal acceptance is about as interesting as the braying of a wild donkey from inside a basket of straw, of course).

I really don’t see a sharp difference. The Torah was given to the community and the contract was signed with it, so the reasoning is that the community is what determines how it is to be observed.

Still asking: is the reasoning a consideration of the Holy One, blessed be He, and because of it He now commands each Jew to follow all sorts of directives, or is it a consideration for each Jew on his own?

I didn’t understand the question.

It says in the Talmud that one must sleep in a sukkah. So now, at the end of the day, is the Holy One, blessed be He, directly commanding me, “You must sleep in a sukkah,” and He chose to command me with this command rather than another because this is what was concluded in the Talmud, which the community accepted upon itself (and if the Talmud had reached a different conclusion, or if the community had accepted a different book, then the Holy One, blessed be He, would have commanded me differently)? Or did the Holy One, blessed be He, command only the Torah, and now a person on his own thinks that it is right and proper to obey the community’s consensus just as it is right and proper to obey the commands of the Holy One, blessed be He? If in your opinion this distinction is not well-defined, maybe you could explain why. A practical difference for someone like me, for example, is that if there is a specific will of the Holy One, blessed be He, then that is something important even if I’m not interested in the considerations behind His wanting and commanding it; but if this is an independent reasoning (the way I think about morality), then I definitely judge how reasonable those considerations are.

What a person thinks “on his own” is also valid by virtue of God’s will, like morality. If I were to think that God’s will is that I should not sleep in a sukkah, then presumably I would not sleep there, under either possibility. But that is fairly hypothetical, because I really have no way of knowing that.
In short, the Holy One, blessed be He, expects us to obey the interpretation that was accepted as Jewish law, even if it does not hit His original intention. But that is so long as I have no other information. If in some way it is clear to me that this is a mistake, then we have entered the law of one who errs in a commandment to obey the words of the Sages. Here there is room for discussion.