As a clarification, you don't need elfeed-tube to subscribe to YouTube feeds (channels or playlists) with elfeed, or to watch the videos with mpv. elfeed-tube only adds text to the feed entries, in the form of more video metadata, transcripts and synced playback with mpv.

Also, mpv supports lua scripts for a variety of actions on YouTube (or other streaming) videos, such as showing you YouTube's recommended videos in the video player, clipping and downloading videos, sponsorblock and submitting sponsorblock segments, and so on.

I've been doing this for almost a decade, and I do recommend it. In my experience, just importing my YouTube subscriptions into a feed reader was a positive experience. I've had a daily digest of mostly interesting videos and rarely (if ever) the urge to browse YouTube.

But with YouTube's recommendation algorithm out of the picture, it does mean that you'll have to find some other way of discovering new channels.