I just don’t see these problems. I’m yet to reinstall MSFS and, with the one exception of trying to get the xbox / MS store to actually see the update on day of release, the process has never really been an issue to me, even if it’s a little cumbersome (i.e. separate store + game + marketplace updates)
My internet is OK, but not awesome (UK-based, 40Mbps down) but the updates typically max it out and rarely take longer than an hour or two - fortunately they are released at the end of my working day, so I just fire it up while I’m working and let it run.
I’ve seen a few others have issues with it wanting to redownload the whole thing, but this isn’t something I’ve ever seen. For reference, since day 1 I’ve always had the game data directory in a completely separate location to the game itself (D:\Games\Non-Steam\FS2020\Official…) so that I can move / backup / monitor this myself. Perhaps this has avoided issues with the MSFS installer losing track of the data and insisting on a re-download?