Rear wheel not straight because of worn out dropout?
This almost exclusively happens because of external cam quick release skewers not clamping the wheel tight enough.



Bike manufacturers love them because they're light, cheap, work fine most of the time, and nobody ever questions them when buying a bike. But they never have as much clamping force as internal cam types, and the problem is exacerbated once they're weathered and worn. There are some out there these days coming on some bikes that barely work or don't work. I know it sounds conspiratorial, but it's sadly true. There's a certain bike model I've been dealing with where the skewers just go in the trash, because the resting spot of the cam produces so little clamping force that using the front brake at any speed readily shifts the axle around.

Another possible issue in the same vein is wingnutting down the skewer instead of properly clamping it.

You could try some metal filler on the frame plus a good skewer, like any Shimano. Glob the filler on more than needed and then use files once it hardens to take off the excess and recreate the axle groove. The upshot here is that nice skewers put on so much clamping force that the frame isn't going to receive the kind of stress that caused this. This is a little bit of an experimental solution so I wouldn't expect a shop to do it.