Just bc you can’t lift your arm doesn’t mean you can’t exercise your muscles, a good PT will accomodate and gradually buildup resistance, and over time you’ll find more range of motion and strength to add more weight.
Mine started me laying on my back taking stress off shoulder and going thru several motions with just weight of arm, which was not fun, big day when I got up to holding a 4lb weight thru same motions.
Took me 11 sessions over the course of a couple months to get good enough to keep the regimen up on my own. And that’s with 2x as many home workouts in between. Not everyone has my shoulder issue, some need surgery some don’t, but even with the majority of tears I was told you’re still probably gonna need to go thru PT first to be a candidate for surgery.
I saw u lift some heavy sturgeon in the boat this spring, my couch doc degree tells me your shoulder isn’t a disaster.