Lifts end in failure without any burn, struggling to break ~1 year plateau
I worked out a lot in my early 20s, stopped for a long time, and picked it back up ~2.5 years ago.
For the past year, I haven't been able to improve my lifts at all. I lift to 'failure,' but the failure is just my muscles giving out. I don't get any of the burn or soreness I used to associate with failure, but I physically can't do another rep.
I go to the gym every day on a 4-day cycle: three days with 20 minutes of cardio and 50 minutes of strength training (back/biceps, legs/shoulders, chest/triceps), and the fourth day is an hour of HIIT.
I'm 5'7" and was around 147 lbs when I first plateau'd. I tried increasing my calorie intake and protein from 0.8g / lb to 1g / lb, but I just gained 12 lbs without any improvement in lifts after a couple of months. I also switched up my routine with different exercises twice, but also no improvement.
My goal for building muscle was to lower my BF%, so I eventually just said fuck it and went on GLP-1 to meet that goal. I'm now down to 125 lbs and have largely maintained the same weight with ~one less rep. Now I'm back to trying to increase my lifts, but I have no idea what I need to be doing differently.
Am I missing something obvious here?