The short version of Clement’s complaint is that the snap packager installs from a proprietary Canonical-specific source. If you want to distribute snaps, you have to set up an account with Canonical and host it there. While the underlying software is still open source, the snap packager breaks with long tradition of having the distribution of the software also being open and free.
Snap packages also tend to be slower to run, in part because they are actually compressed filesystem images that need to be mounted before they can be executed. Some users find this element to be especially annoying from a system maintenance standpoint, as every snap package you install will actually show up as a mounted filesystem.
If we download youtube-dl directly from the developer’s website, the script only takes up 1.7 MB on disk. But the snap package of the same program weighs in at an incredible 91 MB. It’s clear how this problem would be compounded as more snaps are installed.
That said, it seems unlikely that snap packages will be embraced by the larger Linux community. Currently, the repository back-end is actually proprietary. While Canonical does allow for companies to create “branded” versions of the Snap Store, it’s just a cosmetic change and doesn’t allow you to run your own server.