As I age, my success is not great with improving my own hamstring mobility, so I obviously don't have any silver bullets, but I can offer some observations from my own experience, and you can decide if any of this applies to you.
If I do static mobility work without a heavy dose of dynamic mobility work first (ideally a full workout), I'm wasting my time. I get no gains from it and sometimes end-up with jacked-up hamstrings. This is apparently pretty common for aging desk jockeys.
I, too, have decent squat depth, even when things are so tight that I can't touch my shoelaces, let alone my toes. When I can barely touch my toes, I can cossack squat ATG. Some people's hips just don't bend forward great, but turn the legs out and things can open up nicely. YMMV. Regardless, if your range of motion works for what you want to do (e.g., oly lifting), don't wreck your hamstrings getting better at something that you might not care about (e.g., yoga).