I was you (20some years ago). I played as a kid and a couple years after college and then left the game (life got in the way) until I retired around age 54. I started playing again and in a year or two got down to a 5'ish index (my distances were similar to yours). That index bounced around in the 4.5 to 6.5 range for a decade or so.
I half way stopped playing around age 65 for a couple years (played a couple times a month). In the last 3 or so years I have started back in earnest (DOB 1949). I have lost a solid 40 yards off the tee since my early 60's. I now struggle to maintain an index under 10 (but with some work and help am currently at 8.9).
In looking back
I got some helpful coaching on coming back to golf (also some unhelpful, to me, coaching as well). I ended up just learning to manage my swing myself. But the helpful coaching was quite helpful
Rather than focus on my weaknesses I focused on 'what would respond to effort'. And I was a stats nerd and probably had more detailed stats than 99.9% of the golfing world (at least back then)
I am a slow learner and don't blame my lack of progress from coaching necessarily on the coaches. But you need to pick carefully and I have no idea how to make that judgement in the general case.
More recently I have utilized @MonteScheinblum online help and that was meaningful (but I am still painfully slow in making changes). FYI, things really had gone badly downhill (even on an age adjusted basis). Had I a chance for a do-over here, I would ask the question "Monte, where were you in 2005". Other than that - no regrets.
dave