I’m not necessarily sure if we need stat un-simplifying per se, but we certainly need more distinction between items in particular between items from different content types.
Having all gear be almost identical is pretty poor design and doesn’t encourage players to do content they like for those rewards, instead it potentially encourages players to do content they don’t like to gear for content they do (ie needing 2k rating in PvP for rewards to be equivalent/better than WQ rewards)
One of the big things I see with current items from raids in particular (and possibly caused due to the lack of different “sets”) is that there is only one of each item for an armour type from raids.
So if mastery/crit is bad for your character the piece is just horrible and you need to get it from elsewhere.
Previous expansions would have say a mage, warlock, and priest appearance and items had different stat allocations to them so there were 2-3 different bracers with different stats you could choose from etc from the raid alone.
So as a Mage you might take the Warlock appearance shoulders, with priest appearance legs, and Mage appearance gloves so that you get better stat allocation.