You can use a custom template to remove the 'interested' option from your RSVP events! Here is a video that takes you through the steps:

Here's how to remove the 'interested' option from your RSVP event landing page. Click the "Event page" icon for your RSVP event.
Scroll down to the "Custom event page" section and click "Custom templates" to create a new custom template, or to edit an existing template.
Once you have a template open and ready to edit, scroll down to the block tag section and copy the block tag for {{block:rsvpform}} then paste it into line 101 (if you have not previously e...