Hodge podge!. With basic comprehension of Boolean algebra, that's practically all you need. Translating gates into math is all it takes. Knowing about CMOS / TTL, timing constraints, CDCs, IP, clocking, drive strength, power domains, etc. and other aspects of digital electronics can come later.
I've helped high-school & college students for my company for many years who barely understand digital electronics and they program FPGAs all day. Even people without engineering degrees. Sure they don't understand some of the "meat", but if they want to learn in time they will. They can code in any of the HDLs out there like no other.
There are lots of ways of skinning a rat.
I agree, that you could learn FPGAs first.
I'd still prefer to teach, at least basic digital electronics first. Especially gates and flip-flops, and worry about FPGAs later.
I guess it is a bit like machine code, which (probably), use to be taught at educational establishments.
But these days, they would probably dive straight into high level languages, and have little or no coverage of machine code.
Which is fair enough, since machine code is getting increasingly rare, these days.
I guess you could say, the same about discrete digital logic devices. They are still around. But if there are a number of digital devices needed, it is often better to just put them all into FPGAs and/or microcontrollers, these days, production cost wise.