This used to be a lot easier, Youtube had an export function to OPML and you could just import it.
Its quite useful being able to follow all your Youtube channels with your RSS reader if you want to pick which you want to watch then also Metube and the browser plug-in makes it a right click and select to send it for download.
I took it as a chance to weed them out. I went through each one manually and made a choice whether to keep it. Went from ~260 to 130.
I also unsubbed from each so as to make yt unusable, so I wouldn’t be tempted to go there, unless specifically looking for something.