PSA: It is important to read all the software update buttons. Even if you ignore the first big Tahoe ad (same will apply to pads and phones), and just choose to "update", the upgrade to Tahoe is checked by default and the button will read "Upgrade".
This disingenuous practice which Apple has been practicing for years now, has resulted in many non-consentual OS upgrade.
The roll back process, especially without proper backup can be next to impossible, and the Liquid Glass UI roll out is just latest in failures of a company that false advertised AI, lies in court and dines with dictators and gifts them gold.
On a conspiratorial side note, this company is now fully Fourth Reich compliant, so careful installing anything new that might open up new backdoors.
/rant
With as easy as backups are to do with macOS you should have at least a weekly backup, if not the one you performed before you started the update/upgrade? And unlike an iPhone/ipad when you wipe a Mac it reverts to the initial os that shipped on the device.