If your Snap account is unverified, there seems to be no way to know who created the snap. It looks like I can create an account with the name of any company and distribute stuff in their name, including malware.
With something like AppImage, your users know that the AppImage is actually coming from you if you host the file on your domain. Then again, AppImage has its own drawbacks. But at least, if Slack put an official AppImage on its homepage, I'd be able to download it. Installing a Slack snap from the account of "Felix Rieseberg" doesn't sound to good to me (https://snapcraft.io/slack). If you dig around, you can see that Felix Rieseberg does work at Slack, but for this big a company, that just looks fishy IMO.
Your closed source app can shove it.
I suppose I should stop using Linux then, because I occasionally play games from Steam.
edit: btw, I agree with you on the "attitude" thing. There should be more commercial options on Linux desktop.
affiliation: tech lead for the snapcraft tool and linux user since 1999.
Application Bundles (GNUStep), AppDirs (ROX), Flatpak (formerly xdg-app), and AppImage (formerly Klik).
But Canonical invented a fifth anyway. Forgive me if I'm skeptical that change will actually occur this time.
Also, in that category, you forgot Gobo.