Moving the whole building while the Flash moves a truck was, of course, supposed to be funny because everything in the movie was desperately trying to be funny. Having just watched MoS again and watched it very closely, it was clear JL was trying to move away from anything realistic or meaningful on the grounds that audiences were taking that as boring and depressing.
But to the specific feat, I think you nailed it. Something like that is just really obvious that the building couldn't hold together so it's very four color. Had he done that in the Donner movie, it would have been different because the whole style of presentation, at least once he is grown up and in the uniform, is that it's got some wonderful touches of "romance" not just in the boy meets girl sense but also that it's a romanticized world of fantasy. But the buildup of MoS and B vs S was that this world is striving for a lot more realism. And, suddenly, at almost every turn, JL wimps out and compromises the vision of what has been set up to make absolutely sure that everybody loves this movie and they think the way to get everybody to love it is to insert a laugh track. That's basically the equivalent, just throw in joke after joke after joke because that must be the only reason the Marvel movies work.
The building thing actually did get a good laugh in the theater though. But I do think stuff like that, that worked more when children were the main audience, just doesn't work as well now.