That's actually quite a useful feedback because as a non-vim user
Not really, what would be useful would be for a vimist to list the missing/erroneous functionality to make a minimal usable vim like UI (hint hint @howdev :grin:). Then you can determine the scope of the problem instead of chipping away at an edge case at a time and it remaining unusable. We all know you love a challenge, (mentioning no ctags by name) so knowing the size of the job would be helpful.
Knowing you have to re-implement every piece of editor.c [minor exaggeration for effect] due to edge case semantic differences in how things work is important. Although its (literally) many decades since I used vi/vim in anger, from my memories I have my doubts that it will implement as a simple UI wrapper around Scintilla and existing Geany functionality, so I would be interested to see what is required. And of course Vim has changed significantly in that period, hence needing to tease out details as above to reach the [conclusion](https://github.com/geany/geany-plugins/issues/1060#issuecomment-773775126) of what semantics need to be different to those of existing Geany functionality.
And if something is broken, everyone should be allowed to say so.
So long as they say _what_ is broken, and I continued to work with the OP to tease out the actual difference between vim and vim plugin in detail, and not simply in negative terms. I don't see it as discouraging reports to steer them away from simple negative statements to providing useful information.