looks to me like a junction box in the wall.
Is bad idea, but I have just textured over them and paint.
Your so called patch looks to square to me and like a cover and not a patch.
It is kinda camouflaged, but still not buried in the wall and accessible if needed.
So question is, is it really just a crappy patch, or it is a cover to a junction box?
It's hard to tell from just a pic but you might be better off taking off the patch and starting over.I have used the wall span patches and if they are done right they work quite well.Start by sanding it and see how flat you can get it.If you can get it close enough to mud it, go that route.
Charlie Daniels painting and repair