I'm going to have to disagree. Myself and my immediate friend group (6 of us) have all been playing Halo since CE and we all enjoyed the Infinite campaign. Just waiting for the full co-op release to play it again together. Like you said, it's obviously not true for everyone but honestly I think most people enjoyed it.

Metacritic scores are pretty good for the game in both the critic score and the user score. Plus, people who are dissatisfied with a product are much more likely to go online to complain about it compared to someone who was satisfied going online to praise it. I think the reddit/Twitter bubble makes it seem like the game was more poorly received than it actually was.