It worked OK in legion because I still felt my character grow in power over time.
It worked horrendously in BFA because any "upgrade" was actually "this azerite item is much weaker than your existing gear due to you not grinding enough AP/this azerite item doesn't have the right dps traits on it/this item has the right dps traits on it, but the wrong defensive trait, making the enemies scale up to your increased damage and make you feel weaker/you're really not sure plus they might retune that trait so you stuff it in your bank with your other 50 and by the time you actually could use it to its full potential you've got 7 more/you finally get a piece with the right corruption but you can't use it without killing yourself for another 8 weeks so you likewise shovel it into the bank with the others and encounter the same problem again."
TL;DR Legion good BFA bad borrowed power system.