If your site uses collections you need a CMS plan. If it doesn’t you should be able to downgrade if you remove collections and bindings.
Please include your site’s Read-Only Share Link with your question.
A read-only link allows the community to view your project without making any edits to it and help diagnose your issue or provide feedback.
If your project has custom code or layout issues on the published site, please share that URL/URI as well.