Prior to 2015 I doubt you could pull the average person off the street and get them to accurately describe what DND looks like to play. Not so much anymore.
Accessibility isn't just rulesets. Its being able to see how the game is played☆, which wasn't out there in easily accessible abundance until 2015, and it still isn't for the bulk of games that aren't DND. Unless you've been made aware of them and explicitly seek them out, you're not going to be exposed to anything else.
Frankly in my experience unless you've got a voracious reader, most people aren't going to learn any tabletop game by reading a rulebook. They'll learn by watching others play and/or being guided as they play for the first time. Hell, DND was the first tabletop game I ever learned differently than that, and I still really needed to watch and be guided in my first bout with it.
☆and incidentally, this is why one of the biggest problems any game can inflict upon itself is not being clear about procedures and emphasizing their use.