I find gym schedule changes can be very disruptive. Even small ones! It is really hard when there are major differences.
If it is a tentative schedule, have you mentioned to the coach that this schedule is much different than you expected, and explain your difficulties? Maybe you are not the only family that is not happy, and maybe they will change something, if they hear enough complaints?
That said, as long as my kids have been in gymnastics, practice for some groups starts as soon as kids can reasonably get there after school- so, around 3:30-4:30, with other groups starting practice more like 5:30 or 6. Depending on a person's work schedule/commute, any of those times might be impossible to personally drive a child to gym. So, this does not sound like an unusual problem to me. Most parents work, although of course some have more flexible schedules. Many families need to arrange a carpool situation to make it work.
We have not had to carpool for gym practice much, but we have for school. BIG TIME. It is amazing sometimes once you start asking around how things can work out. It might not even be another gym family you find to carpool with, it might be that there is a parent at your dd's school who is happy to bring your dd to the gym, if you can take thier kid to something some other time, or you can instead trade a night of baby sitting, or tutoring, etc?
Obviously there may be a factor I am not aware of, like the gym is an hour away from you, or something. But if not, it sounds like the gym is one your dd would be unhappy leaving. The major issue is getting her to practice at 4:30. The earlier start time may or may not be a solvable issue, but I would suggest look to solve that problem before deciding there is no option but to leave the gym. If that problem is solvable, maybe you will find that overall, this practrice schedule works out ok for your daughter and family after all.