The problem is, only a small percentage of the playerbase do savage and ultimate. Plus if you’re doing it on PF, you find the good players got BIS and stopped playing months ago so weekly PFs are bad, plus it’s hard to get groups after Tuesday so you just don’t bother and have nothing to do.
IMO there isn’t enough incentive (rewards etc) to do old content and very little “normal” relevant battle content to do.
Therefore, if you like raiding, what do you do? At least mythic type dungeons would have filled some gap.