Guardians 2 is going to go down like Empire. People thought it was only "so-so" in theaters but as they digest it over years I think most people will find its the superior film compared to GoTG 1. GoTG is a "funner" film, for sure--its a light action adventure, while Guardians 2 is a lot heavier and deals with interpersonal drama more. So if you're coming from Guardians 1 it can feel off putting. But I think, as said, as it ages people are going to slowly shift and see it as a great film.
Rewatching it now a few times I can safely say I like 2 more than 1, and I love 1. But the family theme in 2 is so well executed, and the resonance of Peter realizing who his father was and then losing him after cementing himself as the father of his new family? Shit was well done, and really impactful emotionally. The movie does not get enough credit for it because a lot of those aspects, again, I feel were covered up by people looking for the GoTG fun, light adventure vibe (Which there is plenty of and I think it kind of distracted from the deeper parts of the movie...But those deeper parts flourish on rewatches when you can stop and think about it.)