When speaking of Math class, are you ignoring everything up to pre-calculus or do you think everything from addition flashcards, times tables, and long division is useless? I'd argue those exercises are invaluable. Seeing two numbers and just knowing the sum is always faster than plugging into a calculator.
This is the same fallacy that people make when they learn a new language, so they pick up anki spend a ton of time on it and most burn out, some don't, but neither see any real benefits greater than if they just spent that time on learning the language. The fallacy comes from the fact the goal of learning isn't to finish problems quickly, but to understand what is trying to be said or taught.
For example you claim that addition flashcards and times tables are invaluable, but you don't specify a base, in base 2 you have 4 addition flashcards, in base 100 you have 10,000, clearly understanding addition isn't related to the base, but flashcards increase as base increases, thus there is a relation, implying of course that understanding addition isn't related to the number of addition flashcards you understand. Oh but of course they aren't invaluable in understanding addition, they are invaluable in understanding concepts that use addition, cause ... why exactly? You saved 1 second finishing the problem that you may have understood before you completed that addition step? You didn't have to "context switch" by using a calculator? Students who don't know the sum often give unused name and go back at the end of the problem and solve it later. This behavior is of course discouraged since students can't understand variables until much later if ever and not knowing something you were taught represents the failure of the student and thus the teacher, school, government and society.
Infinitely better is learning from someone who speaks the language.
A 30 minute solo tutoring session once a week for a month, in a no distraction environment (aside from a snack), even just working through homework, is more than enough for most students to go from Fs to As for multiple years.
Personally I have dyscalculia and to this day I need to add on my fingers. Still, I ended up with degrees in physics and computer engineering. I don't think those things you mention are useless, but they never worked for me so I don't view them as invaluable.
