@asimovthedon, did you figure out why that happened, and why it didn’t affect everybody?
I’ve installed multiple times, both with the Steam version and the MS Store version (though I suspect Steam doesn’t have their own FS servers so we’re all hitting the same servers regardless), and have never had such an issue, despite having installed MSFS probably 20x more times than most people. It’s never taken longer than roughly a half hour, including both the Steam version and the MS Store one. (That’s an estimate just based on being here at my “desk” while it was happening, not a measurement.)
I’ve got gigabit Internet, but I’ve never seen MSFS use more than about half of what is hypothetically available.
I have seen radical changes in speed (like from 400mbps down to under 1) when downloading some payware components (say a purchased aircraft or airport), but I have no explanation for that at all.
I’m looking forward to tomorrow when the patch comes out to see if the whole world hitting their servers at the same time makes any noticeable difference on my end. It never has before, but this will be my first time patching with the MS Store version.