Spawning shells and user folders is tricky. The thread from the shell may be a different user, so it won’t have (direct) access to the user-specific folders.
Now in your snippet, PackageFamilyName and Id will have to be hard-coded or made variable. If hard-coded, the script will more than likely only work on that particular machine since part of the name looks to be generated (like seen in the example here): How to open UWP apps from the command line on Windows 10 (addictivetips.com)
What you could also try is going with a SendKeys type of approach, where you send the Windows key, then the name of the app and Enter. That is probably very brittle though (and may not work to start with).