This really bothers me as someone who can easily spend up to 10-15 hours a day playing mythic plus alone. Now in Dragonflight players are being forced to play old dungeons with normal regular mythic plus seasons.
I think it's too forced of idea in my personal opinion. Repeating old dungeons at large (which is what mplus requires from you to do anyway) can be extremely demotivating factor to continue playing WoW for me. The fact that I've done them to the point of mild PTSD. It doesn't look to be any optimistic to be honest. Only new things should be mainstream, and old dungeons should be buried away and left to timewalking instead.