Horrible? Really? Most reviews I saw put it as one of better Marvel movies.
I liked it more than I thought I would. It's much faster paced than all movies until now and that tempo starts literally from the beginning and goes until the end. The action is non stop but with enough explanations and dialogues in between for me. After all it is about a war, per se. I'd recommend watching it and deciding for yourself. I liked all the details which I don't want to spoil, and many, many unexpected scenes which they were able to hide from trailers and leaks. They also developed Thanos as a proper villain imo.
All people that I know are satisfied with the movie, and I don't think I heard anyone saying that it's bad. I think it's one of the better Marvel movies. Not the best, but it's up there. It's much better than Ultron, for what it's worth.