Vanilla WoW was good, indeed.
I do miss the "danger" when running around the game world.
It wasn't uncommon, in fact it was very normal that people died at least once or twice during the first 5 levels in the "tutorial zone".
Not that the enemies were that difficult.
But if they outnumbered you they could easily kill you.
The game was hard in a fair way imo.
Over extend and chances are high that you (and your group) will pay for it.
A system like this gave people options to tackle encounters.
If you wanted to you could take it nice and slow, pull a mob at a time.
Or you could go ham and pull multiple.
Ofc multi pulls got easier the higher level/better gear you had.
But this also gave players time to get comfortable with their class.
Learn the strengths and weaknesses they had at their own pace.
I was a bit thrilled back pre Heavensward when they talked about how they had increased the difficulty of the overworld mobs for HW.
But I honestly couldn't tell the difference which led to being a tad disappointed.