If all else fails, change your mindset. Use RSS feeds to pull new videos from your subscriptions into a reader (like Feedly). That bypasses YouTube’s UI entirely, giving you the spirit of old YouTube without the actual app.
If you dislike the modern web interface, you can use browser extensions or userscripts to force a classic look. how to get old version of youtube
: This extension provides a menu that lets you choose exact recreations of layouts from 2008 to 2021 with a single click. If all else fails, change your mindset
Example search: “YouTube 14.12.52 APK” (late 2018, last version before modern layout). If all else fails
You cannot technically "downgrade" the website itself, but you can use scripts and extensions to change the look and functionality.