So first off, I am by no means purporting to be some kind of expert on China, especially as I cannot read or speak any Chinese dialect to be able to actually experience their media, news, culture etc.

That being said:

China is not trying to erase those other languages

If the entire European union /somehow/ decided to standardize language to... I dont know, Esperanto, or Interlingua, and as a matter of policy, forbade schools generally accessible to the vast majority of public school children from teaching the language of the country they are from, would you consider that 'erasing languages'?

As to Taiwan ...Self determination is not an option.They are going to be in the US sphere of influence or the Chinese.

Well, I think there is a large difference between self determination and being in a sphere of influence.

Ukraine is now very, very much more obviously in the NATO sphere of influence militarily, and the EU's sphere of influence economically. But they still have self determination. They can elect leaders, vote, blah blah liberal democracy, but the self determination does functionally exist.

True they are not an island, but they were considered to be a weak, liberal democracy, contested by two powerful spheres of influence... should the ideal situation for be either loss of self determination and formal annexation/absorption into Russia, or perhaps Poland?

Conversely, (though also not an island) the Palestinians have barely had any real self determination since the Nakba, as they have been made, and are still, so totally beholden to Israel economically that even though they do have their own government, its decisions and goals are constantly rendered functionally void as they have no real effective means to alter their situation meaningfully on their own.

They have even less functional power to use their self determined leaders and government and quasi governmental organizations to meaningfully act on their own, and are basically totally economically beholden to Israel, and basically in military terms are caught between Israel + US, and various other Middle Eastern states and organizations.

Should they give up what little self determination they have left, and formally just join Israel (who certainly will not let them do this as they are currently busy genociding them) or a nearby Arab state (all of whom will nearly certainly also not do this?)

You can go even further with your logic here.

Should the Kurds give up their struggle to carve out a formal right of self determination and simply acquiesce to being ruled, divided, by autocrats who claim the territories where most of them live, or simply all migrate their territory within one bordering autocratic state and just hope to not be oppressed there?

The point I am trying to make here is that I do not believe that the general principle of a small, relatively weak people should simply acquiesce to a total loss of self-determination simply because they are massively influenced by larger nearby powers.

If, as another commenter mentioned to me somewhere in this thread, the Taiwanese people actually use their self-determination to voluntarily integrate with the PRC, I would respect that.

But just using the logic of 'they have powerful neighbors so they must obviously give up their autonomy to one of them' is not compelling to me at all.