Don’t go too far the other way as to say NOTHING is taught. Merely, not enough. Another factor I would say is that technology has reduced how much folks need to know, for example, the aerodynamics on newer aircraft are much better especially at the edges of the envelope (high altitude, low and high speed), and FMCs that can give you an answer in seconds as to what altitude you can maintain right at that moment.
hence why things like Mach tuck were something one flying a Lear 24 would have to be very aware of; but someone flying a Lear 60 or 75 could probably know little to nothing about, and the aircraft takes care of that for them if they get near that performance edge. which is unfortunate, as back to basics should really be a thing.