their the thing. I may not like every rpg on the market. I'm not telling people not to play them. Or assume that because I dislike a rpg then everyone else will or should. Too often in the hobby their is no middle ground. It's the same logic and I use the term loosely. When someone says a rpg will fail because they don't like it. I may dislike some design elements of Pathfinder. I don't think it's going to fail.
While I like complexity it's not what the current or even some of the older generation like imo. If they did companies like Hero Games would be making a profit. As it stands HG is not dead but on life support. There more uodates on 3pp support then any new product. Gurps while still supported by Steve Jackson Games relies more heavily on Munchkin for their profits.
Developers of tabletop rpgs have to go with the trends imo. If it's more complexity then they publish rpgs with that. If it's rules light the same. I don't think were every going to see a return to rules heavy rpgs. I'm not saying they will disappear. Just that for better or worse rules light rpgs are here to stay. Nor can I see a negative. Short of the rules light rpgs not being as comprehensive. Even then I sometimes wonder if they really are rules light. Instead of one big book like Hero System 5E they spread the rules over multiple sourcebooks. It feels lighter because it's more spread out.
I'd be really hesitant to ascribe failures (or slumps) in individual game systems to something as high level as rules heavy/rules light.Over the same years Hero and GURPS haven't been doing great, Pathfinder has been growing. And SJG has been supported by Munchkin for years, IIRC. There may well be other trends or internal reasons that explain their decline.
Rules light games are here to stay, of course. They've been here to stay for decades. Depending on where you draw the line, the early 80s at least.
Rule heavy games are here to stay as well.
Different people will still like each and some will like both for different things. Which games are most popular will change and that may make it look like rules light is winning or rules heavy is, but I doubt it's nearly that simple.