I would say it's just more playing golf. I went from less than 2 years ago never breaking 100 to a 4.1 handicap. The only difference is I played A LOT more. I did not increase distance or anything crazy, I just do not duff shots and have better feel on pitch shots and putts.
I think most golfers except true beginners have hit a great drive, a great approach, a great chip and a great putt at least once, I feel that playing more makes those types of shots happen way more often.
I have tested new equipment and my very old equipment from my starter set along with my current 3 year old driver, and i still top out at 220 in distance, and lessons or range work have never done anything for me. I have seen some very ugly swings have great results so I think trying to fit in a mold is not ideal, if you just go out and play golf A LOT you will improve and your score will lower exponentially.
I think a lot of people want to fight their swing and are obsessed with distance gains. I could not tell you how many times in my leagues i see a guy boom it 50 yards past me, then i watch bemused as he pitches it 3 times back and forth across the green. Getting better scores and playing good golf is from making shots, and lessons nor range work or even a driver that goes 50 yards further will never help you with that, only playing golf out on the course where you need to execute and make shots happen and put in the time that you have done almost every shot on a real course, not in a no pressure practice setting.