Jim, I may have found a strategy that keeps the spirit of original programs but allows for adjustments, especially for those a bit older. Unlike others, I don't mess with exercise choice, sets or rep schemes. I have used it for a few programs because I get stuck in between as programs for average people are too easy, but I am below the baseline of groups like the Strongfirst forum.
Basically, you keep the same programming, but you repeat some workouts, days, or even weeks. For example, for programs that are linear like power to the people barbell, you add a step or repeat a workout, like the linear step approach to barbells before adding weight. Or you slow it down. A pushup program that calls for adding a rep a day, you may add every second day or whatever. For a program like the giant, you could do it for 6 weeks instead of four before attempting 1.1. A bodyweight program that gets progressively harder, you might repeat the first foundational workout for a week to provide a stronger base before starting the program. I did this with a pushup program. Repeated the standard pushups before moving to diamond pushups, for example. For the Giant 1.1. I couldn't get the 8 reps in for every set last time, so I did half 8s, then 7s and finished with 6s. But this week I did all 8s but my volume went down. I am sure it will be back next week. I just needed the extra workout. That is still progress in line with the program progression almost as written.
Rather than adding exercises (adding front squat to the Giant is a bad idea the lower body workout you get from heavy cleans is deceiving) or even taking some movements away. Repeat or slow the program down but don't change the way the progressions are written. This has been my approach for programs that I think keeps the spirit and intention and progression of the original author while making it a bit easier on my 52 year old bones.