Hi.
Cryptomator Desktop was designed to work with as many online storage provider as possible.
The best way to achieve that is to rely on their existing connection/sync process and not implement various different interfaces to directly connect with them. Many providers don’t even provide any API or WebDAV connection at all, so these providers would not work together with a direct connection cryptomator app. This is why the desktop app is designed that way.
However: when it comes to mobile apps it is often not feasible to have a vault local, or to download it completely, so in this case the design was made with focus on data transfer and local space usage. and that lead to the direct connection design. Yes, this means that the mobile apps are not usable with every storage provider out there.
Besides that, both design need to have the vaults added first in cryptomator before you can open a vault. Your screenshot only shows the process of connection to your storage provider. It does not connect to a vault. You have to add vaults behind these connections.
If you want to access your cryptomator vault on your desktop directly online, see here for a solution: