I do get what you're saying but...
First of all, full disclaimer: I'm not especialy a fan of Dan, but my girlfriend is, so I'm very, very familiar with GameGrumps, StarBomb, NSP and TWRP.
I totally get why people would not like it. Synthwave is not for everyone, the animation style got so many influences that it starts referencing itself at some point, and it's not original in the first place. All of those are valid critics, and I totally accept them.
But that's not why the video was made. The goal never was to make an outstanding piece of art, it was to provide content for the fan community, and it's done by the fan community itself. The GameGrumps are youtubers, they need the hype, they need content, that's how it works. And let's be honest, even if it's not original, there's a real effort that fans can appreciate.
In the last month, the gamegrumps and affiliated have released 4 animated video clips, with original artworks, from various artists. (it's not their usual pace, of course, it's because they released a new album). Outside of big studios, they are providing work, PAID work, to artists who do them. They're giving jobs to fans, to produce content for fans. That's something pretty much no one else does.