Yes if you dedicate your time you should be rich, I agree.
I think casual players never will be able to reach any meaningful percentage of legendary armory usable for them though.
The game is bloated with too many different gear items (stat combos), so the "exotic" armory would be essential to ease that pain.
I think legendary gear is essential because it is the very definition of quality of life in this game.
I think legendary gear should have only one advantage: its visuals.
I think collecting exotic gear (stat combos) for the exotic armory could fill the gaps of missing pieces in legendary armory.
Almost all players could benefit from it, so why not?