First - everyone’s capacity is different; science discovers averages. There’s freaks who can do 20 sets and people who can do 5.
Over time you may be able to increase your tolerance slightly but recovery is ultimately a limited resource. Sleep, diet, and reduced stress outside of the gym are the only three things that I’m aware of that will help. When I had a job that basically was 2hrs a day, my diet was clocked in, and i was sleeping super regularly, I could do a lot more in the gym than I am now. I’m repeating a cycle from several years ago and I think my fatigue is more than just age.
The other area you can improve recovery and overall capacity with is performance enhancing drugs. That’s something I don’t really know too much about, but that’s the way I’ve heard it described - you heal faster, stronger.
Aside - last I read, ice baths are counterproductive to muscle growth because they reduce the inflamation that signals to growth. They’re useful for competitive scenarios where recovery is prime, but they don’t help with improvment. By all means keep doing it if you enjoy it. My strong preference is for a sauna!