I feel you.
I am also really burned out on having to farm up things on multiple characters again and again to be able to get to some cosmetic stuff I cannot get on my main character (because of gear restrictions or faction / race restrictions or the inability to do all professions on one character). I have stories in my mind for my characters, but currently they are all in a limbo because Shadowlands killed my motivation to do anything. The grind was just too much. I somehow managed the 15+ Keymaster achievement in the 1st season on my main, but did not even try on any of my alts I got to max level and somehow decent gear in that time. I also get sick and tired when I even think of leveling characters again, did not had that feeling ever before. Sure, leveling has been quite boring most of the time, but it just went by, especially when the Pathfinder limitations finally went away. In SL, it was too little and too late and I cannot even find motivation to unlock flying in ZM on my main. When I think about Legion, where I have been playing alts galore, BfA has already been a depressing condition, but I have at least managed to level up most of my Horde alts and one Alliance (about 29 max level characters in total) and even get 2 allied races to max level or at least their heritage set. Now I only have 5 characters at max level and that's it.
While I find some ideas of Dragonflight interesting and I even know which one of my alts to delete to get me an Evoker character for my collection, I really don't know if I will play the next expansion or not. And I have been playing WoW since the end of 2005 almost without any breaks (except for one burnout phase in MoP).