One of the most iconic weapons in all of gaming is the Blue Turtle Shell from the Mario Kart series. The weapon is just so devastating and frustrating when you're in first place, but probably the most satisfying weapon ever if you're in second place. But what would Mario Kart be like without the power of the Blue Shell?
If Yabuki says something feels off and like "something's missing" then I'll trust his judgment on the matter.
The Blue Shell picked up its dreaded reputation after making its debut in Mario Kart 64. The game introduced players to the first-place equalizer. It was a weapon that was usually available to anyone at the back of the pack, or in some rare occasions available to second place if they were so far behind that it wasn't even funny anymore.
The Blue Shell only targets the person in first place. Some trickery could be used by the person in first place by slowing down and allowing the person behind them to move up into first place so that the shell would target them instead.
Of course, in games like Mario Kart: Double Dash the tactic of switching with second place was a bit more difficult because there were usually two people per kart instead of just one, and so someone on the other team would figure it out and make preparations to thwart your plans.
The foils presented in Mario Kart: Double Dash didn't last when Mario Kart Wii came along and it was back to every karter for themselves. This resulted in the Blue Shell gaining even more power because everyone was out for themselves, and the tightly compacted tracks from the Wii version of the game meant you had to keep first-place in sights but out of range from the explosion. It was a far more frantic version of Mario Kart than previous entries due to the tighter corners and more narrow track layouts.
Nintendo, however, greatly nerfed the impact and power of the Blue Shell by the time Mario Kart 8 came along, making the tracks wide enough so that avoiding a first-place after-effect was pretty easy, and they even tossed in the horn item that could be used to stop the Blue Shell from making impact.
Given the balancing out of the Blue Shell's power thanks to the introduction of the horn, I would say that it's still fine to keep it in the arsenal of items available in the Mario Kart games. But, it doesn't matter anyway because Yabuki doesn't seem to want to get rid of it either.