To be clear, I agree. Containers on Linux are very weak security boundaries and should not be considered safe sandboxes for untrusted or dangerous code. In fact, post-Spectre, only physically independent hardware unattached to the network should be considered a reasonably safe sandbox.

However, something is better than nothing, and it's just not true that there's no difference between running something from the AUR and running something in a "confined" snap. There is some crap in the way at least.