lsp-mode maintainer here. I may assure you I know how the traditional elisp is written and I simply dont like it. Happily lisps allow you to write in different styles I can tell you that a lot of people find lsp-mode's source code more readable(in addition to being faster). To give an example of the differences in the mindset: Emacs core developers have `first`, `second` and `rest` deprecated in favor of `car`, `card`, and `cdr`. I will do the opposite.
Of course, there are problematic sections (so do eglot) but keep in mind that `lsp-mode` and emacs-lsp organization has ~10 times more code and contributors.
> The thing with the whole "entry barrier" point of people who want Org-mode development to happen on Git(Lab|Hub) is that they miss the point: I don't want more contributions, I want more engaged contributors, more committed support of any kind.
If you want more engaged contributors you need more occasional contributors. Some of them will grow into core contributors or co-maintainers. Putting more obstacles is not the way to filter the out less engaged and keep the committed one but way to discourage the potential valuable contributors. That is why being on github where practically all of the OSS is happening is important(even being is gitlab won't have the optimal effect).
Of course, there are problematic sections (so do eglot) but keep in mind that `lsp-mode` and emacs-lsp organization has ~10 times more code and contributors.