> am I just slow / a poor listener?

Don't fall into that trap. You like what you like. Bach wrote hundreds of pieces. There's no reason for anyone to "get" or "like" them all, or indeed any single one of them.

Personally, I like some of the piano and cello pieces but they only get played once or twice a year. Whereas his vocal works like the St John Passion and Ich habe genug from cantata BWV82 get played a lot. Everyone is different!