I honestly just hated it because it touted cooperative play, and the guy in the back did absolutely nothing. I can't even make any sense of the "forcing two players into one cart" logic. It felt slower-paced, yeah. And heck, I could more than forgive that if they had something interesting, but it seemed to me like it was too few tracks, and you could only access them through Grand Prix. No free play, just tournament play. What the hell? I mean, even Super Circuit (one of the best out of the Mario Kart franchise, IMO) had more options. The graphics also felt short than they could be, and hell, it just wasn't any FUN. When Mario Kart games stop being fun, you know there's a problem.
I'm honestly done with the Mario Kart franchise. I'll go back to MK64 anytime, but I seriously prefer stuff like Modnation Racers, Sega All-Star and Crash Team Racing. Hell, get Naughty Dog to make Mario Kart. They'll make it interesting again.
The front guy was the driver while the back was weapons. One thing I'll say is that the idea of the Double Racer system was an interesting idea. It could've added a whole new strategic element to the game. But once again, the items unbalancing & distribution essentially made that possibility null and void. The main problem with it is that certain characters were better than others, especially when it came to the whole "specials" dealio.
I didn't play enough of Double Dash to remember if you could have 4 players racing at once, each having 2 choices of characters, or if the game forced you to always play team mode, 2 vs 2. If there was no option for either or and was just the latter, then yeah it was a stupid idea, just like it is in MKWii's unplayable Battle Mode.
Overall though, I'll disagree with you on the fun part. Except for Double Dash, which again I hated, the Mario Kart games are still fun. I'll be the first to admit that the series is a spiky shell of its former self, as again I consider Mario Kart 64 to be the perfect kart-style racing game, but it is still fun. As I mentioned before, Mario Kart DS was actually a pretty decent karting game, and the best one that came after MK64. Sure, the problems I mentioned still do exist, but the items felt more powerful (especially Red Shells), the level designs are easily among the best in the series, the music was pretty solid, the handling was much better, the customizable icon thing for your kart was genius, and they got rid of the Double Kart system. Plus, even though the kart imbalance is still slightly there, there are still multiple multiple kart options which all have a pretty good chance to win. Sure, some karts are slightly better than others, but it is in
NO WAY as blatantly unfair as the 3 Bikes are in MKWii. MKDS's battle mode would have been fine if not for the blowing into your mic to blow balloons thing.
Mario Kart Wii was definitely a step back from Mario Kart DS. The item imbalance is much more apparent, as well as the distribution and gimping of said items, and if you master one of the best 3 bikes, you never need to use another again. The level designs weren't as good as DS as well. It's still fun, but only if you are playing with multiple people who are your friends, and even then the problems of the game can be apparent.
With Mario Kart 3DS, I hope they at least go back to the Mario Kart DS engine, since I know they'll never go back to MK64 style.