I could give or take the ability requirements for multiclassing (since in 5e all spontaneous casters no longer really need their relevant ability if they use spells without attacks or saves anyway, and it was weirdly arbitrary for how loose the system generally is), but as for the spell slot issue... I guess we'll either have to wait and see exactly what the heck was done there.
As for the rest - it feels a little baffling that after 3 years of EA and supposed player feedback gathering the very systems that the feedback would have been based on have been altered so strongly - supposedly based on the in-house tester feedback instead? I don't mean to smear the tester's job as it's hardly a valued one in the industry (wrongly so, as so many releases showcase recently), but when for so long the EA players have been asking for stricter rules and a faithful adaptation of the more baseline RAW a Tasha-like homebrew gets pulled out at the last moment and concessions are being made to ease the experience for newcomers and passers-by.
Attempts at appealing to the more general crowd have almost killed RPGs as a genre once already, hence the renaissance in the mid-10s, and seeing it done again would be quite unfortunate. Turn-of-the-millenium CRPGs wore their (varying, but still) complexity on their sleeve and had dedicated cult following because they targeted that specific niche, and BG3 is supposed to be an heir to one of such games. I have to agree with Tuco and his exhausted proclamation here, I am afraid.
