Allvit derailleurs shift fine. Does it really matter if it were to shift a couple microseconds faster anyway? It's just a utility bike, meant to get you from point a to point b without breaking.
When they don't shift acceptably it's usually a matter of: chain caked in sludge, bent derailleur hanger, bad initial adjustment, lack of lubrication of the cables, pivots, etc. Any 50 year old bike is going to have at least a few of these problems. Fix all these issues and, like I said, they're fine.
This would be a fine bike(s) to learn bike maintenance on.
A few decades of repair by unit replacement has caused a shift in perspective. It seems to me that a lot of newbies think it's going to be easier to simply bolt a new component on than to do regular maintenance. Many if not most new/modern bike components are not designed to be maintained. Use it till it breaks, then buy a new one. That's why we get such ridiculous notions as buying an old Schwinn, and putting new parts on it to 'fix' it, when all it really needs is basic maintenance and a tune up. Apparently taking mechanical things apart, cleaning them, and putting them back together is scary for the new generation. /
