How to get back to previous update as new one is terrible

Apple has never permitted downgrading, nor should you choose that approach even if it were allowed (which it is not).

About Apple software updates - Apple Support

If you tell us your specific issues, perhaps we can assist you.

Rolling-back to an earlier version of iOS/iPadOS is not possible. All System Updates are digitally signed by Apple - and can only be installed whilst the digital signatures remain valid. After release of a new iOS/iPadOS version, the immediately preceding version continues to be digitally signed by Apple - however, usually within a few days, Apple will revoke the digital certificate with which the earlier version is signed.

Perhaps consider that iOS/iPadOS updates include both functional and essential security updates. Restoring an earlier version of the OS would expose your device, privacy and data to emerging and known security threats and vulnerabilities.