Dear Blizzard,
due to the fact that:
a) Your designing team has ignored all the feedback of all the previous months of shadowlands and thus you are constantly nerfing and buffing things ON THE LIVE SERVERS
b) Several DPS classes are completely useless and require fixing to be appealing to do the content YOU have created (e.g. Rogues in raids)
c) Several Tanking classes are completely useless forcing people to use only Demon Hunters in high mythic keys
d) You have constant lag in the areas that the world boss spawns
e) You have constant problems with the login servers
f) There is a lot content still to be seen with the covenants etc.
It would be wise to delay 9.1, delay adding content and delay flying. You will simply mess the things further more.
There are enough things to be revised and fixed and I do not think the core community would like to see the addition of further broken stuff that will lead to constant nerfs buffs and changes on the LIVE realms.
Release content when you are ready, at the moment you do not seem so.
Regards,