Confluence does not (to my knowledge) provide out of the box activity reports for all spaces as you have seen
For those who are not aware here is a link https://confluence.atlassian.com/doc/viewing-site-statistics-123043962.html
So to achieve your requirements you need to look at extending Confluence through the use of a plugin and some are described here. https://confluence.atlassian.com/pages/viewpage.action?pageId=154239308 and if you have access to the underpinning database https://confluence.atlassian.com/display/DISC/Obtaining+Confluence+Instance+Metrics.
I hope this helps.
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