1. people are always going to be able to use themes that are not available to snapped apps. This one we can't fix, but we do have plans to add "theme" snaps. Not really a snapd issue, although some support to make things automagic might be needed.
2. some snaps that could use themes haven't taken the extra steps to do so. Again not a snapd issue, although we are encouraging people to do this work (and have tried to make it as simple as possible).
I'm setting the bug to Invalid for snapd, which doesn't mean the bug itself is invalid -- it's just not something that snapd itself can fix.
There are (at least) two aspects to this:
1. people are always going to be able to use themes that are not available to snapped apps. This one we can't fix, but we do have plans to add "theme" snaps. Not really a snapd issue, although some support to make things automagic might be needed.
2. some snaps that could use themes haven't taken the extra steps to do so. Again not a snapd issue, although we are encouraging people to do this work (and have tried to make it as simple as possible).
I'm setting the bug to Invalid for snapd, which doesn't mean the bug itself is invalid -- it's just not something that snapd itself can fix.