I had a 25+ year gap in my D&D gaming. It started again when I moved to the PNW and met a couple in their 40's who took gaming very seriously, and started playing with them again. They introduced me to something I had overlooked: comic book stores that had Walmart-sized gaming arenas! Now I'm hooked again, but with people who care more about story than treasure. The amount of work my DM puts into backstory is insane, and he asks the same of us (well, not insane levels, but a commitment to character).

TL;DR - Playing D&D as an adult, with adults, is vastly different than playing as a teen.