In regards to Groot I can understand the criticism being expressed. I think for instance the breakout scene where he is tasked to get the prototype fin back to Yondu Gunn stretches out the gag to the point where the scene drags the pace of the film to a crawl in order to satisfy the gags in question. First he gets a pair of underwear, then he gets a weird space creature, then he grabs a ravager's eye to which Rocket requests they leave it because it'll be funny (and as a call back to the original movie), then he grabs a desk, then he grabs a human toe, then they stop to clarify Groot's opinions on hats, and then FINALLY Kraglin brings the fin to Yondu directly.
I'm not going to suggest those moments aren't individually funny, but I do believe that Gunn goes overboard indulging in that gag to the detriment to the pacing of the scene as a whole and squandering the effectiveness of the gags in the process. Had he been more judicious cutting some of those gags in favour of sticking to the rule of three it could have felt more succinct, punchy and funnier overall. (Not suggesting he has to strictly follow any rules of comedy, only that he could have afforded to edit and tone down some of the repetition).
One might also lay this notion at the rest of the comedy in general so it isn't specifically a Groot issue, but when he is the focus of a scene he is utilised in a manner that often falls under these issues and exacerbates audiences patience in the process.