Nope, we could not disable the starttime of the appointments.
I did some research and tests about your issue and found that the starttime you mentioned is related to the columns settings in View > View Settings > Columns like below and these columns are enabled by default. I'm afraid that it is by design that we could not hide start time of your calendar. Compared with Week/Day view, Week/Day view shows start time on the left of the current view.
Here is a similar issue, also for your reference.