Hi Miles,
That stall usually means a corrupted pack or cached data is blocking the load. Do a clean pack and cache reset while keeping your worlds safe.
Close the Minecraft Launcher and the Xbox app. Press Windows + R, paste this exactly, then press Enter:
%localappdata%\Packages\Microsoft.MinecraftUWP_8wekyb3d8bbwe\LocalState\games\com.mojang
In the folder that opens, open the minecraftWorlds folder and copy it somewhere safe like your Desktop. That is your backup.
Go back one level to the com.mojang folder and rename these folders so the game stops using them on next launch: resource_packs to resource_packs.old, behavior_packs to behavior_packs.old, skin_packs to skin_packs.old, development_resource_packs to development_resource_packs.old, development_behavior_packs to development_behavior_packs.old. If any of them are missing, that is fine.
Now clear the app cache. Press Windows + R again and open %localappdata%\Packages\Microsoft.MinecraftUWP_8wekyb3d8bbwe\LocalCache.
Delete everything inside LocalCache. Do not touch your backup.
Start Minecraft for Windows from the Launcher again. The first launch may take a little longer because it rebuilds the cache and will redownload any Marketplace content as needed. If it opens normally, you can copy your worlds back only if you had moved them out. Add packs back later one by one to find the one that breaks the load, if any.
Tell me what happens after this exact reset. If it is still stuck, I will move you to the next fix.