Gosh. This looks like an old landscape azalea that was stepped on or run over or hit by a falling tree!
Given the condition it is in I'd not root prune if for at least a year while it gets healthy. However, I'd recommend you completely, gently, root wash it if you haven't already after blooming and get rid of all the old soil. Then plant in an entirely new media to help it recover.
Here are a couple ideas for media,
1. 50/50 rough peat/sifted small old pine bark with a bit of manure tossed in if you have it.
2. 90/10 Kanuma/pumice of the same size. medium or small will work
3. Ye Olde Nursery azalea blend = 50/50 rough peat/perlite. Watch this mix as it can dry fast and then look like it takes in water but hasn't. If its dry, submerge it.
Good luck and let us know how things go.
Cheers
DSD sends