Clinton, pithy or not, I think you're right.
I was slightly competent at barres with my index finger, but I stopped playing for a while, and when I started again, my barres were crap. Apparently the ONLY way those muscles get strong enough is by actually doing the barres. My middle finger is just rotten at it, so I guess that's next.

Is your thumb directly under your finger on the neck?
It seems like it's possible to compensate for a wimpy barre finger by overcompensating with the thumb. If the finger was stronger, perhaps you could hold it straighter, and it probably wouldn't take much work to do the barre chord.

I don't know much about playing guitar, but I've had enough problems which are either fresh in my memory or I'm still working on them.