Both Confluence and XWiki are huge and your experience is subjective, so it really depends on which parts you'd want to see improved. General improvement should not be made through extensions, it should really be done directly in the product. Quite some customers have pushed for improvements over the last months, for instance we now have page ordering in the navigation panel as a core feature thanks to their valuable feedback.

So don't hesitate to share your feedback on the project [1] (generic feedback is interesting to read but specific stuff is more easily addressed), read previous feedback [2], ask questions on the forum [3], chat with us on our community chat [4] or even report bugs [5]. See also the roadmap to see if something important to you is already scheduled [6].

If you have money to spend, also know that XWiki SAS [7] offers consulting and support and we address customer concerns. We also sell "Pro" extensions (with free trial) that cover some features that are expected by Confluence users, among other things [8] (while we sell these features, it's not open core. It's still (truly) open source: you can get the code under LGPL and all).

[1] https://www.xwiki.org/xwiki/bin/view/Survey/ProductFeedback

[2] https://www.xwiki.org/xwiki/bin/view/Main/Feedback/DownloadF...

[3] https://forum.xwiki.org/

[4] https://dev.xwiki.org/xwiki/bin/view/Community/Chat

[5] https://jira.xwiki.org/

[6] https://www.xwiki.org/xwiki/bin/view/Roadmaps/

[7] https://xwiki.org/

[8] https://store.xwiki.com/