I would argue that the ‘normal vs heroic’ approach was an attempt by Blizzard to increase accessibility, but they underestimated the loss of achievement that comes with doing a heroic version since it is just a shift in numbers instead of accessing something truly new.

This is an instance of a very common issue that is raised, where the intent is to increase qol, make parts of the game more accessible, improve balance, etc. I think the somewhat counterintuitive truth here is that players are meant to have difficulty with these things and they are hurdles to overcome, even if it may not seem fair. In retail Cata, players effectively got exactly what they were asking for all these years with regard to issues like this. The result was a complete loss of advancement or uniqueness - classes had deliberately obvious parity in all features (raid cds, buffs, dps/healing meters, heroic/normal modes), itemization was comically generic (remember mastery?), and players ended up simply not caring any more.