I guess I find it more acceptable than most, at least in theory. I mean, you already have most of the big-name heroes saving entire worlds regularly, because that's what they do. So when you put them on a team together, the implication is that they need to do something bigger, and reality is reasonably big.
On a less meta-fictional level, you also have a lot of obsessive reality-destroying godlings wandering around the universe pissed off at their last defeat. The surprise in-story should be that this doesn't happen continuously and there's rarely more than one threat to time-space at a time.
So, in theory, I'm OK with it. In practice, the stories tend to be pretty thin (Marvel's go-to is still to defeat the villain through the power of the scavenger hunt, I believe, while DC's is to mess with the timeline even more to prevent the adventure from happening) and the results are really the star, the stories just being excuses for a new status quo the latest writers decided they want because they can't be bothered to continue someone else's story.
To be fair, most of the stories I loved as a kid were on that scale, so I see the potential in it. And if I want a story about people in uniforms beating the crap out of petty criminals, I can talk to cops, so I don't have much interest in reading comics about that sort of thing. It's when it's used as a tool to write out unpopular stories, institutionalizing the idea that history is whatever the writer says it is without just saying it, that it gets on my nerves.
The stories that piss ME off are the "board room of doom" stories that were in fashion for about ten years. You know, where the villains (or, increasingly, the heroes) spent most of an issue following Robert's Rules of Order discussing how brilliant this plan is. You know what? I have meetings at work. They're not fun. Reading about other people being at meetings? Unsurprisingly, LESS fun.
