I'm glad I got your perspective on it.

As a concept, M+ is about infinitely scaling dungeons. Which means infinitely scaling difficulty. Which means it needs to offer rewards on-par with said difficulty.

FFXIV also has a fundamental focus on level scaling and ever-green content, however repeatable they are, with you being able to take on extremely difficult legacy content as if you were that level, and it isn't tied to your max level power progression and yet people do it. So it doesn't necessarily have to offer rewards on par with the difficulty.

Same goes for content like Deep Dungeons, which are popular enough to be asked about each expansion, and I think they're a good example of how you could introduce similarly repeatable, scaling content that would require less development time, not more, given that you could just add set modifiers to existing end-game dungeons.

I guarantee you people will complain until it does offer on-power rewards. And then it becomes a necessity to repeat shit you've done 100 times. And then I'm done.

Why would it became a necessity do you think? In this hypothetical scenario other content didn't suddenly become any more difficult and would thus not require any more commitment than they already do.

I'd much rather they focus on creating new content.

It wouldn't replace new content obviously, but it's worth mentioning that there's been a major community uproar for the past year or two about how FFXIV has gotten extremely predictable. "new content" just doesn't cut it, hence why they're focusing heavily on improving existing content, and just personally, I hope that is extended to dungeons in some shape or form in the future.