Hi @Yiru Chen ,
Yes, it is a known scenario in SharePoint Online that Content Organizer functionality is not working with SharePoint Modern experience. As far as I know, Microsoft has no roadmap to roll out this feature currently as Microsoft encourages users to use alternative modern features in Microsoft 365. Document routing can now easily be done with Microsoft Power Automate Flow. This is in contrast to significant time and effort that one must spend when setting up a Content Organizer with various rules and routing maps.
If an Answer is helpful, please click "Accept Answer" and upvote it.
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.