I never saw it, but based on Mr. Enter and JoshScorcher's reviews, I believe I know why.
While the animation is impressive and looks just like the show, it's probably the only good thing it has. The voice acting was OK, but the best were Pinkie and Bubbles.
First off, Rainbow Dash is WAY out of character in that one. She wouldn't care most of the time what Twilight was doing, not that she hates her, she wouldn't take stuff from her friends and such, and (just imagine that Tanks for the Memories
doesn't exist/consider this came before) when she destroyed Ponyville, by accident of course, destroying their homes, businesses, probably seriously injuring and I'll even go far as to say KILLING ponies, though that wouldn't happen, it was done as if she just wanted to go fast, acted all selfish, and didn't care about anypony else (Josh also pointed out that even though she is a daredevil, she practices AWAY from others, which is another thing Mr. Enter pointed out, Rainbow has common sense even if she's not the most intelligent). Plus she also got off scot-free (If you see Josh's review, you'll know what I mean). I know people have compared Tanks to the Memories
, but at least in that one she was worried about her pet and even "I'll Fly", she did admit what she did was wrong (and Josh liked that episode). And she did learn a lesson about hibernation there, while in DR, her only lesson she learned was "don't take things that don't belong to you." I've only heard one person say Dash was perfectly in character in DR, but they didn't get her character and claimed she sold Fluttershy into slavery (taking care of a dog with another caretaker is NOT
slavery) in Trade Ya!
, and she was a criminal
Well if she truly was oh so a criminal, then why do the Mane Six stay with her? But this is some guy who claims he has "realistic views" (aka IMO looking WAY TOO DEEP INTO A CHILDREN'S CARTOON THAT ADULTS ENJOY) yet sounds completely hypocritical when he says Fluttershy in his opinion not developing is due to fact, not opinion, and says you should not be "subjective" when reviewing, what a stupid moron. But I digress, back to Double Rainboom.
Two, most of the humor is just random references and such, such as the
in the potion smoke, and there are all sorts of pointless references there that weren't needed, such as some Portal cube somewhere, Twilight stands by the fire left from the Double Rainboom and a certain film with a certain Delorean's theme plays, and so on. Plus there's also Transformers references towards the end.
Third, Zach and the trailers lied. The trailers made people think that Double Rainboom was going to be the first fan made episode entirely accurate to the spirit of the show, but then we had the Powerpuff Girls (good show though, I love it) segment in there. Josh pretty much said it was someone's bad fanfiction put to animation, and it was I'd say. Also, Mr. Enter said there was nothing else in the episode that previously suggested crossover. Rainbow's OOC behavior adds to this, and that whole thing with Pinkie using her breaking the fourth wall powers as a Deus ex Machina; that never happened in the show.
Plus, Zach is a huge dickhead. You may also have heard that Double Rainboom was taken down because he wanted to "move on", but THIS is what actually happened and why:3.bp.blogspot.com/-4qnld62yNNY…
A way better Rainbow Dash episode than this is Mysterious Mare do Well, and I'm not trying to start a pointless debate, but that episode honestly is not as horrid as people say it is, to me anyways (and Josh didn't even think it was that bad). It did teach a better lesson than this thing, and Rainbow did act more in character (one thing I will say though is in there, she understood her friends' intentions even if she did get embarrassed, and her friends weren't acting as antagonized as people say they were), but I digress yet again.
Those are my reasons why I think everyone hates Double Rainboom. If you like it though, that's fine, and I respect your opinion.