I would agree. The “Focus on Similar” feature isn’t working well. It looks like it uses the main blue tags for the album, but not all recognised. For example if you use it from an album in your Qobuz library it must be seeing “Classical” only (all Qobuz albums whether baroque, romantic or whatever are classified as classical!) then it brings up my whole library of 1300 plus albums. On the other hand when I use it from an album in my own library it can be more successful - e.g. from an album of Beethoven piano concertos it shows my other 130 or so albums of concertos (mind you baroque to modern!), but not always! e.g. from an album of Bach’s complete organ works it once again shows my whole collection, presumably ignoring the baroque and organ tags but focused only on the Roon Classical tag.
So I don’t use it as it is not useful. Pity. I’ve just discovered another post on this started in 2015 Focus - would be great to have the default focus a little tighter - like your 'Similar To', 'Influenced' and "Followed' lists and a comment from someone from Roon within it 2016 saying it would be worked on but might take some time - it certainly is.