I don't think companies like Meta, Alphabet or even Amazon are extremely overvalued. Their growth in revenues and earnings is still very solid, so even if A.I is a no show their earnings should continue to do fine (I'd even add Microsoft to the list). Sure stock price might slow down significanty but it can easily add 10% yearly for the forseeable future. Its much less than what we're used to, but its solid growth that has not much to do with A.I.

And I totally agree people should forget about the s&p 500 returns we've seen in the last 15 years going forward, it would probably be less (though I have no crystal ball, but regression to the mean seems likely).