People forget how hard this stuff was when it first came out, now that they’re 60 levels higher and can solo it.
It took five months between release of Molten Core and world first Ragnaros kill. Five months! Mythic Jaina took less than a week. If you count Heroic as the release, Jaina was still only a couple weeks.
More debuffs will help a lot. Knowing the fights will help. The availability of tier 0.5 will help with MC. But classic raiding difficulty will still be at least as hard as mythic is now.
Honestly. Bring back raids which take months for the world firsts.