Going by Wikipedia numbers this thing is more powerful than the Gamecube.
Gamecube's got a 486MHz cpu, the 3DS is powered by 2x 266MHz. This seems faster to me considering we can't compare clockspeed because this is a new CPU vs an old one, right?
"Pica" is clocked lower than "Flipper" (166 vs 133MHz) but I guess being more up to date it is at least as capable (and I guess the lower resolution helps).
And the 3DS has 64MB of RAM, the Gamecube had 48MB.
It is right between a Gamecube and a Wii, where's the problem? They'd be stupid to put a huge CPU etc in there. When you design any product you have to remember you are selling to customers not to yourself.