I last looked at this a year back and at that point, it was still not addressed and was a topic in the Office 365 uservoice (started back in 2015!). But I have not been able to find anything regarding updates (or tracking) for this much needed feature. Does anyone have any access to any updates on this?
P.S. this is my research on the topic. In Sharepoint Online, you can get to Site Web Analytics Reports page (below url append) but that will indicate that Usage Logging is disabled on the tenant.
Another place was Security and Compliance tile under Office 365 for Audit log search (needs to be enabled by tenant admin), but I am not seeing that as being evolved into meaningful OOTB usage analytics solution (more of logging/auditing)
Office 365 user voice for Usage reports: https://office365.uservoice.com/forums/273493-office-365-admin/suggestions/7194558-usage-reports-for-sharepoint
Old (Apr 2016) MS response for not supporting Site Analytics in SP Online: https://answers.microsoft.com/en-us/msoffice/forum/all/web-analytics-in-sharepoint-online/fee15d10-00e5-4496-89e4-ccad70ef1802