Ok, first thing... at 43 rest is gonna be very important. Sorry but as we get older, it takes a lil bit longer to recover from those ass kicking workouts, granted you are natty...are you natty or on cycle?
Second, some programs/routines might work better than others. For example, when i started lifting i was told "heavy weight with low reps blah blah" well guess what...i didnt get shit from those types of workouts. Since my goal was size and gains, i started to do way more volume such as GVT and high reps/sets, and noticed much better response from my body. BUT.. again everyone is different, so you will have to find what you benefit more from.
Back to the first thing, what does your split look like? (Workouts and rest days)
What does your eating/diet look like? Im gonna throw this out there, and it goes against all bro science and traditional thinking we have been taught. Your age, at your age it might not be wise to consume mass aounts of calories, 5-6 meals a day like we have been taught AT YOUR AGE. Why? Bcuz from alot that i have read lately, natural hormones and GH are blunted from food consumption as we get older, at certain times such as pre workout and post workout, which in turns leads to fat gain, not muscle mass. I put some of these theories to the test myself, such as eating 3-4 meals a day and not 6-8 like i did 2-3 years ago and believe it or not, im doing waaay better, even with my junk food binges that im known to go about.
Only you can dial in your body, which takes time, trial and error... there is no one size fits all thingy. However you can take pieces of advice from what people tell you, and see what works and trash the rest...process of elimination in a sense. Like i said before, so many variables to your situation.