Min-maxers will always min-max, the rest of the population would be more inclined to do Mythic+ dungeons because even if it goes horribly as long as they slog through it they would complete it. Then we have the fact that the non-optimal classes/specs could actually get runs. Timers are incredibly dumb mechanics to include in anything that takes longer than 10-15 minutes. Real life happens, to some more than others, so you immediately exclude anyone that can’t set aside 30 uninterrupted minutes. Then there is anxiety/stress, frankly put there are a lot of people playing mmo’s that don’t want tons of pressure/stress. Take away the timer and those people can clear it in time no problem, but the second you have a timer ticking down it causes anxiety/stress to ramp up to the point where they don’t do the content.
There is a bunch of reasons to get rid of timers, but there is only 1 reason to keep them and that’s players being exclusionary. They want to feel special and can’t have anyone else feel special so they gatekeep. That is of course toxic, which is one more reason to remove timers.
IMO they just need to make soft timers, something for min-maxers to go for but doesn’t exclude everyone else from completing it.