I think the problem is rather simple really.

There is literally no difficulty curve in this game and hasn't really been since ARR's launch.

In 2.0, the last few dungeons all had teeth and would happily punish you if you disrespected them and many of the mechanics used were lightly toned down versions of what you'd later see in the hard mode primals. By doing your end game dungeons, you were pretty much training yourself for hard mode primals. Thus the populace in general was reasonably prepared for the end game's gatekeeper aka Titan HM.

By comparison, recent Expert Roulette dungeons have been face rolls across the board with the vast majority of mechanics being entirely ignorable currently, yet the entry primals are significantly more complex and are a pretty solid challenge when tackled in ilvl appropriate gear.

In some respects, O1S is actually a pretty good lead on from dungeons and rabanastre. The problem is, it's the right sort of encounter in totally the wrong place, it really should have been the very first Primal of the expansion, with a more complex encounter taking it's place as the first Savage step.

The other approach of course is the have the Expert dungeons throw watered down primal and savage mechanics at you. Of course this requires tighter communication and planning within the encounter teams and might not be reasonably feasible in mid tier patches.

I do think it's something that needs to be addressed tho, the current design philosophy is just making significant swathes of the community complacent and lazy in their play style which leads to a horrible culture shock when they try to dip their toes into the raid scene. That in turn leaves a bad taste in peoples mouths on both side of the coin which in turn helps reinforce the whole casuals vs raiders thing.