Is there a way to back up my macbook to icloud?

No ,  iCloudcan automatically store your photos, calendars, contacts, notes, passwords, and more. And it includes iCloud Drive, which can store documents, desktop files, and other files of your choosing. To access those files, you just need to be signed in to iCloud. Other cloud-based services are available from third parties.

The Mac includes all system files from user library and system library , including inbuilt applications , so time machine is required to back up Mac .

You can read this support page for help backing up your Mac: How to back up your Mac - Official Apple Support.

That support page also goes through how to back things up to iCloud vs Time Machine.

I hope this answers your question!