Why do you get that impression? That’s not true at all.
I once tanked all the time on each and every tanking class. Then BFA happened and Mythic + got crazy. I walked away then and now it looks like for another expansion with these nerfs to tanking, even with the new Mythic + changes I will not be returning to tanking in any capacity. Once it was my jam and I had fun. Then someone said no more fun for you and ruined it for me.
As a tank you really take on a lot of responsibility IMO. You’re the guide, the leader in most cases. Expected to know where to go, when to go there, how fast you need to do it, and to do it all within a damning time limit.
Ya I see longer queues but not just tanks. There will be healers that don’t want the added pressure as well. Sure there should be risk but at the end of the day this is a game and supposed to be fun. Once it gets stressful, why keep playing? If I want stress I will go back to real life.