Why should we? I'm sorry but in my opinion movie critics generally only love the stuff that does really really bad at the box office, or that runs 5 hours long because it captures the "beauty" of what movies used to be about. Movie Critics are generally older folks very much out of touch with reality, and they think waaay too highly of themselves. Last year I went through the MSNBC archives on movie reviews, and I didn't agree with a single review that they posted. Everything they hated I loved and vice versa.
On balance, all movie reviews could just be- explosions, great, story- incoherent, but it doesn't matter. A + film.
Where you draw the line is up to you- if ultimately an incoherent, corny story is propped up by larger than life CGI, then you can 'take it for what it is'- however, you wouldn't subscribe to that in every instance.
You could after all make a Pearl Harbor flick and lousy it up entirely with a gratuitous, superfluous love story, cardboard characters and a clinical, generic feel about war- hey, wait a minute..

Critics
criticize films- that's what they do. You can take their viewpoints and balance them with what you like or expect to see.
Personally, I think Michael Bay sucks- I think his films suck, there are film students who have made more interesting and entertaining films with smaller budgets than his soulless tripe. Simply having the money and near inexhaustible backing from major studios doesn't in itself create a better experience- it may even cause these types of block buster directors to get lazy once they've stumbled onto the formula which churns out bank, but will never win critical praise, but what happens are those people who point out that after a while, these films tend to feel like the same experience as any other in this class are viewed as elitists like film critics.