Sorry to ruin your point but GotG was a team up film about five obscure characters and yet most people liked it very much.
BvS is a team up film with well known iconic characters, I don't see the problem here.
That misses the point. There could never have been any ''gravitas'' (the word that Rorywan used I think) attached to seeing a bunch of unknown characters coming together to form what happens to be a team precisely because we never knew these characters separately. At least the general movie-going populace, maybe comic book followers did. I myself had never heard of them until that movie, so I never regarded it as a team-up in the same sense as I did The Avengers. They might aswell have been a team by default.
Personally I'm not saying that BvS will be impossible to like as it is, I'm only saying that it could potentially have been better than it will be if these characters had had solo films beforehand.