We had exclusive gear and no alternate progression paths for 12 years before Legion. It was fine.
You don't need top-end gear if you're not a top-end player.
Alternate progression systems could be a good thing for the game... but they haven't been yet. AP sucked, Azerite sucked, Covenants suck, Garrisons sucked, and probably a few more I can't think of at the moment. I can't imagine Blizzard are going to suddenly figure out how to make them work after failing a half-dozen times already.
Just to be clear here, you're asking for all gear progression to be obtainable from mindless, boring world quests. This would literally kill the game overnight.