Posters are still there.
It’s xls export that’s disabled, as well as export from photo library
First parameter starts with an ? and not an ´&`
So correct line would be:
{MY-PMS-IP-HERE}:32400/library/metadata/124552/thumb/1649212325?X-Plex-Token={MYTOKENHERE}
All of it 
Edit: And forgot…
To export posters and or art, use a custom level like:
