As a sunlight sensitive person, I will be sad if they remove sunlight sensitivity

[Psyren]

Oh, no, they're not there yet; they're just making kobolds not at all resemble the MM creature so far, and making Kenku less interesting.

The playable Kobold is in Volo's actually, not the MM.

Regarding Kenku being less interesting now - as a wise person once told me, "you may want to be more careful to label when you're sharing your opinion, rather than stating facts, because you seem to be stating your opinions as facts and then using that as argument to why contrary opinions are wrong, rather than matters of taste."

So the "optional rule" is not permitted anywhere? You can't have it both ways: either the "optional rule" is in play, or it isn't. Now, the middle ground is that some tables permit it, and some don't. I don't know AL; does it not permit the optional rule?

It's permitted but you're not forced to use it. Think about it logically - if you didn't purchase Tasha's, how would they force you to make a character with its contents? The whole point is to encourage you to buy the book if you like it, but to still allow you into AL if all you own is Core. Hell, you can play AL if all you have is the free Basic Rules PDF.

Still noteworthy that they made every new race have it. I will be (pleasantly) surprised if MotM doesn't codify it as being the default for all races printed therein, including any reprints.

Floating ASIs is the default in MotM, yes. You do not have to use MotM. (I mean, your DM can mandate only the races from that book obviously, but they cannot mandate themselves to be your DM if you don't want them to be. Moreover, there are no core races in that book, so you'll have an option for fixed ASIs until 2024 at least.)

You seem to be under the impression that the people playing PCs dictate what books are used in a game.

If your DM refuses to let you be a Volo Kenku when that is important to your concept, that is hardly WotC's problem.