I usually agree with GI and their evaluations, but every once in a while I absolutely disagree. This is one of those cases.
The thing about Battleborn that I've noticed is that it's very much a case of "love or hate". Matt clearly was in the hate camp, but there are plenty of people (see TotalBiscuit's review for one) who loved it.
This would be a great opportunity for GI to bring back the "second opinion" column they used to run.
The humour is very much in the vein of Borderlands. I think it's actually better than Borderlands, but that is completely subjective.
The action is frantic and chaotic at times, but like with any other game, as you play it for a while, the chaos melts away and I had no issues figuring out what was happening onscreen. No different than Borderlands in that regard.
I know that Matt disliked the character lines, but again, this is Gearbox humour. Love it or leave it - I loved it, Matt didn't.
The game is not without its flaws, as the coop campaign can become frustrating at times, and the story doesn't really make a lot of sence. However, as the intro sets up, the game is very much supposed to be a videogame version of a Saturday morning cartoon. It hits this look and tone perfectly - even if the humour is a little more mature than in most kids' cartoons.
Overall, I very much enjoy the game, especially in split screen. Your milage may very, but I think that Battleborn's biggest problem is the constant comparison to Overwatch, which is a radically different game tbat happens to share a few similarities.