It's a legitimate point that needs addressing, yeah. It's also one not strictly belonging to games - watching The West Wing, you might think that it really only took a dozen people to solve the nation's problems, and the Marvel comics universe is crippled with this issue, to the point of everything being sucked into their weird supermilitary-industrial complex. Mass Effect is still totally the worst at it, tbf.
With games specifically, though, that power narrative underlying the whole thing gets twisted by that kind of thinking. Leveling up and becoming greatest hero in the land means you would normally be able to expand - go from Batman to the Bat Family to Batman Inc., essentially. Which kind of happens in, say Mount & Blade, but that's the rare exception. And in a way that doesn't actually solve the underlying issue - you still being the only one who can solve the world's problems - but it does at least have a more logical progression. Personally I think the 'power fantasy' label is a bit misleading, with a lot of it coming down to a simple desire for agency. The player is able to do a thing that has an effect on the world. Doesn't have to be big. Just has to happen. Sending out minions can have the same net effect on the player, so long as they still feel like they were the one who caused it to happen. Designers are less likely to see the problem simply because "What's the point of making #content if the player can't #engage with it?" There are some games where you're simply not going to access all the content in a single playthrough, either because of choices or time limits or whatever, but that's not quite the same thing, I think. Having a quest where the 'best/true ending' is to just stay out of it would be kind of funny, though.