I'm working at XWiki SAS [1], which provides hosting, support and customization for XWiki [2], an open source extensible wiki you can use for collaboration in a team (among other things). We are seeing many clients coming from Confluence because of the recent price raise and so we have tools to migrate from Confluence. They seem happy. There are ways to customize XWiki to fulfill the specific need of each team if the wiki is a model that suits you. There are a lot of extensions available and you can program in the wiki itself to adapt it if standard XWiki lack some specific feature you'd need.
I don't know Confluence though, so I cannot say how more or less polished XWiki is compared to Confluence.
Anyway, don't hesitate to reach the XWiki community (there's a public forum and a public matrix channel, come say hello!) or XWiki SAS if you have questions or concerns, they'll be happy to answer and you can see whether XWiki would be a good fit for you :-)
I don't know Confluence though, so I cannot say how more or less polished XWiki is compared to Confluence.
Anyway, don't hesitate to reach the XWiki community (there's a public forum and a public matrix channel, come say hello!) or XWiki SAS if you have questions or concerns, they'll be happy to answer and you can see whether XWiki would be a good fit for you :-)
[1] https://xwiki.com/
[2] https://xwiki.org/