Went over to bumbags a few years ago and never looked back.
Bontrager rapid pack is my favorite – just big enough for most local rides and doesn’t move around.
Osprey savu if I need something a little bigger
I hardly ever wear a full backpack now. Probably only ever when bivvyig and I have run out of space.
For those of you who don’t get on with the smaller bumbags, are you still trying to carry everything in them? Bumbags work better when combined with a strategy of strapping stuff to your bike..e.g. bottle in cage, micropump on holder next to bottle, small saddle bag for inner tube and tyre levers
Etc.