https://bugs.winehq.org/show_bug.cgi?id=42457
--- Comment #2 from Austin English austinenglish@gmail.com --- (In reply to Dan Dascalescu from comment #1)
Update: turns out the Gecko installer was stuck downloading. After canceling the download, applications start fast.
Still something worth looking into maybe?
And how do I finish properly installing Gecko?
You can manually download the .msi and put it in ~/.cache/wine/, see https://wiki.winehq.org/Gecko