The progress bars on versions on the classic planning boards was more useful than on the new planning board, simply because it contained more information.
For example:

• grey bar = no issues assigned to version
• red bar = issue to be done
• yellow bar = issues in progress
• green bar = issues done

This was very useful, but has been removed on the progress bars of the new board, which only consist of a blue progress.
I attached two screenshots:
New:

Classic:

Also there is no progress bar for "unscheduled" anymore, which was also useful.

Please bring this back!