That's not the full picture.

The proprietary store backend really isn't consequential. Most websites are, and if you have a modern computer, you've got proprietary firmware running at ring -3. At best, it's a distraction from Snap's real issues.

Snap packages are compressed filesystems, similar to squashfs. When an application is started for the first time, the filesystem has to be decompressed and mounted to the root filesystem, which (depending on the computer) can take a long time. It also litters your mount points with loopback devices.

Snap's sandboxing only works on systems running Systemd. No Devuan, no Artix, no Alpine; the packages will work, but without sandboxing.

The worst part is Canonical's desperate attempts to make snaps happen.

• Ubuntu ships with a modified apt that first checks if the desired package is available as a snap, and if so, installs snapd and the snap package without asking or even notifying the user. Strike that, it's even worse. https://feddit.uk/comment/20490326
• Canonical repackages third-party software as snaps, which has caused issues for the developers who aren't involved in the repackage: https://mastodon.social/@TTimo/111772575146054328
• In fact, they have published malware on the snap store because review practices are shit: https://forum.snapcraft.io/t/exodus-movement-exod/38904
• Canonical has forced other official flavors (Xubuntu, Kubuntu, etc; to note: they're not maintained by Canonical) to ship their systems without Snap's direct competitor Flatpak out of the box. https://www.omgubuntu.co.uk/2023/02/ubuntu-flavors-no-flatpak

...and I'm sure there's more that I'm forgetting about.