Before covid (not sure how parks are operating now so it may not apply) I could join the FOP line at any time from park opening till park closing. I could choose to ride if I wanted to wait in the line.FYI this is NOT a RotR only issue, there are many people every day that are trying to get on FOP, 7D, and other high profile rides that simply won't because the line is too long when they want to go. RotR doesn't have that issue because of the boarding groups.
Same for all attractions except Rise.
And lest we say Rise is some miracle of the ages, the original Star Wars attraction required Disneyland to be open for multiple days straight without closing to accommodate everyone who wanted to wait in line.