Both make you grind them to be able to minmax. Both give you power. Both give you something mostly unobtainable in raiding. While they arent exactly the same they have more in common than not. Spamming islands for ap or m+ for gear is the same concept if your goal is raiding.
You could argue back then that you also get ap from clearing raids and that farming ap was a choice, people would laught at you the same as thinking that farming m+ is optional if you care about gearing and power, m+ is just so far ahead.
Mythic raiding which should reward progression and long term commitment is barely worth doing when I can be 486 right now without doing it and the cap is around 489.
Just the aspect crest issue completly unbalance the contents. Wich is why at minimum if m+ can drop aspects crests heroic raids should too. The great vault imbalance also should get adressed, capping 3 slots with m+ is not comparable to raids at all.