Yes, once you bend/break aluminum or CF "tubes" they are junk.In fact most steel frames are junk also unless you know someone who is handy with a welder(for cheap heavy steel frames), or the frame is so valuable that it is worth sending off to be repaired.It would probably cost $400 to repair/repaint an old 531 frame that had one crunched tube. Most aren't worth $300, so that is it for that frame-same story for Columbus tubing and even more so for Champion tubing since older Japanese frames are worth 1/2(at best) what 531 and Columbus vintage frames are.
Cheap old steel frames are actually the most repairable since they usually break at the old weld, and the tubing is so thick it can be rewelded. Of course, they are worth the least, so you need a buddy withy a welder.
Don't buy a frame based on how repairable it is alleged to be. It is a bit of a myth that steel frames are "easy" to repair, and are safer to ride with heavily dented tubes.$$ for $$$ almost no frames are worth repairing, if you actually pay the repairman what he should charge.
Luck
Charlie.
Part of the reason CF and Aluminum aren't considered repairable is that it is assumed-correctly-that the other welds/joints have been damaged when one tube/joint fails and the frame bends. Steel is a lot more elastic/flexible, so the other parts of the frame are less likely to be damaged(they might be of course).