The delineation between content and systems is nebulous, but I'd consider stuff like Warfronts and Island Expeditions 'content' compared to Azerite being more of a system. Warfronts ultimately just dump you gear at the end, after all. It was a whole bunch of pain points amplifying each other as you did content that wasn't very enjoyable to engage with systems that proved to be headaches.
BfA had a lot going on that was conceptually interesting but fell apart in practice with minimal testing; we saw that with Azerite armor, and I'll always be a high key Warfront hater in every respect in being utterly baffled how they only got worse going from Stromgarde to Darkshore. Then SL came out and had glaring conceptual problems or repeated mistakes that they seemed to think they could solve by just believing hard enough. DF and TWW (so far) have lacked those kinds of headaches, I'm just looking for some actual meat now.