Time Machine cannot backup to iCloud. It will only backup to external storage devices. See: Backup disks you can use with Time Machine - Apple Support
Apple offers iCloud Backup for iPhones and iPads but not for Mac computers.
It is possible to sync data from a Mac to iCloud if you turn on those options (e.g., iCloud Photos, iCloud Drive including the Desktop & Documents option). Syncing has some of the benefits of a backup (and the benefit of being offsite) but is not the same as a backup. Major differences include the fact that not everything on your Mac can be synced and the fact that if you delete something, accidentally or otherwise, there is only a limited time period (30 days in most cases) during which it can be recovered.
Also see the Apple article: How to back up your Mac - Official Apple Support
And more information on syncing in:
Set up and use iCloud Photos - Apple Support
and
Access and manage your files in iCloud Drive - Apple Support
and
Add your Desktop and Documents files to iCloud Drive - Apple Support
Also, a 2019 MacBook Air is compatible with the latest version of macOS Ventura.