It’s nothing to do with individual connection speeds of users.
It’s cleaner planner’s server, and the way the software itself works.
It was probably not designed for as many users as it now has, and my guess is that it’s not possible to speed it up without completely re-writing the whole thing.
Given that once promised features have long ago been abandoned, I would very much doubt there’ll be any update. I think all work on improvements has ceased for good.