No, he's objectively correct. The better team is the team that wins the match, and scoring more goals than the opposition is the only way to do that.
Now, you can argue about the more attractive team or the more exciting team, but the better team always wins, bar only interventions outside of the rules - refereeing mistakes, beach balls on the pitch etc.
Aside from that lone caveat, I also don't believe in luck in football. Were Chelsea 'lucky' that Barcelona missed a number of very presentable chances? No, of course not, because if Barcelona were better then they wouldn't have missed those chances. Similarly your example about Schweinsteiger hitting the post has nothing to do with luck: if he had shot better, he would have scored instead of hitting the post.
Now obviously judging whether Chelsea or Barca/Bayern was the 'better team' over a longer duration than that specific 90 minutes (or 120 or whatever) allows you to bring other things in for consideration - other matches that season, for example. But over the course of the match, the best team is the team that wins.