If you have tracks connected to a VCA fader, and those tracks do NOT have any automation, when you write automation for the VCA track, there is great probability that after some time (saving, working on other project, etc etc) you will find that the balance of the tracks connected to the VCA fader will be changed.
But:
You are good to go then. There’s absolutely no reason to stop using VCAs if you always remember to write automation for the individual tracks.