Reddit had the same issue not too long ago. I remember a popular post where a user described their workaround of creating an account for each field of interest

Reddit had the same issue not too long ago. I remember a popular post where a user described their workaround of creating an account for each field of interest. To Reddit's credit, they did implement custom feeds not to long after, which lets you group batches of subreddits. Not something I'd expect YouTube to do.