There are several reasons why users might prefer to use older versions of the YouTube app:
ReVanced takes an old version of the YouTube APK (usually version 17.xx or 18.xx) and patches it with mods. This gives you the best of both worlds: stability, speed, and modern features without bloat. Youtube Apk Old Version
Google releases monthly security patches. An old version of YouTube (say, version 14.23 from 2018) will have known vulnerabilities. Hackers have had years to reverse-engineer those builds. Using them on a modern phone is like leaving your front door unlocked. There are several reasons why users might prefer