I think at least part of the problem is the half open/half closed nature of Sailfish OS.

Some features/bugs would be easy to add/fix for third party developers, but the change needs to be done in a closed component and only the already overworked Jolla developers are able to do that.

This can also project to testing - since parts of Sailfish OS are closed and developed behind closed doors you can't have a development distro branch going that people can continuously test and report issues. You have periodic pre-releases that might find the bugs too late, resulting in the final release being delayed or bugs being fixed a long time after being first reported (in the next periodic update - if your are lucky).

And the missing public bugzilla only makes this worse by adding more useless work for both the community (which has to use/workaround using a sub par bug reporting solution) and Jolla (combing through the unstructured questions on together and re-filling them in the internal bugzilla and maybe trying to keep the two in sync somehow).

Another problem could be that there is no real working community distro based on Mer (Nemo Mobile appears to be at best on life support unfortunately...) or any known major Mer user other than Sailfish OS for that matter. That would also help a lot with testing, new package and package update integration, etc. Like this it also all lands on the overworked backs of the Jolla developers...