No, no, and no, but I don't need a Ferrari, a fire hose, or a supercomputer, either.
I don't need a Ferrari, either. But you do need enough power for the task at hand, don't you? I hate SUVs but I can understand that some people have a legitimate need for them. And when the firemen come to put out your fire, you want them to have plenty of water pressure, don't you? If you're a genetic scientist, you might need a super computer, mightn't you?
And if someone is coming to help you fend off an attacker, you want them to be at least strong enough to stop him (or her) don't you?
Or maybe there's some way to make sure that people with bad intentions can't get more strength. Then no one would need to have unlimited ability to stop them as necessary.
How do you determine where we should stop improving our abilities and increasing our capacities? In martial arts, greater strength is nothing more than greater capacity. Why imagine that there's some universal "enough" that no one should want to exceed?
Likewise, is there a limit to how "smart" we should be? How tall we should be? How much money we should have? How is strength any different? No one tells an oak tree "You're strong enough. Stop getting strong." It's just natural to develop oneself as far as possible.
Balance in all things. I wouldn't think that would be such a radical idea among martial artists.
It's not. In fact, that's the essence of most of this internal strength training--tuning our bodies for unshakable balance in six directions. Or should we also leave ourselves to be unbalanced to a certain degree, just so we don't carry it too far?
Can't quite see why you feel that there should be a limit to human capacities.