I think infinite farming is okay until you reach a certain plateau. From there on, progression should be more slow and linear (e.g. PvP gear in WoD - grind Ashran to get a full set of honor gear in a day but getting your conquest gear is timegated by conquest caps (unless you got the catch up bonus)). This creates an environment where you can spend a lot of time on relatively low level activities and get rewarded for it without getting an insane advantage in the long term and once you reach said plateau the game doesn't require you to spend huge amounts of time/effort in order to stay competetive.
The fact of the matter is that you can't have both meaningful endless grind progression and a reasonable limit to what players will feel forced to do in order to not fall behind.
So, what they could do is loosen the restrictions on rep factions, flying, low ilvl (on par with lfr) gear and all the other stuff that only gives you a very limited advantage and at the same time tighten the restrictions on the actual high level gear/power progression so that you don't feel forced to non-stop grind m+, WQs etc.
I'm convinced this would make the game much better and soothe a lot of the complains we've heard over the last years. Of course, in-game activities would shift more towards playing alts and there would probably be less time played on your actual main but overall I think it's far healthier and way more satisfying than what we have now.