Don’t understand why but I did the latest update from MSFS2020, now I’m stuck on the loading screen. Ridiculous never had problem before latest update.
I don’t have the Steam version, but whenever I have had that startup issue, which is rare but has happened, I reboot my computer rather than just crash out then relaunch.
Since you are on the Steam version, the one bit of advice I would give you is to not verify the cache. This will make Steam delete the sim, and force you to download everything from scratch.