Almost all of Sondheim's scores are pastiche, so "catchy" is certainly subjective.
If you are an aficianado or just brought up around the music that Sondheim is channeling in a part of whole of his scores, then that's "catchy" to you.
If you're a fan of the tin pan alley then Forum and some of his other more traditional musical theater scores are probably your taste.
Subject matter plays into it, of course, as well. If your partial to people eating other people, then maybe Company...um, I mean Sweeney might be more your taste, no pun intended.
And, I don't think that "catchy" is by any means judgement of how good something is, even if that wasn't the intention of the original poster. Many people do feel that "catchy" music is often facile and predictable, even if it is Sondheim-catchy.
"Fenchurch is correct, as usual."
-Keen on Kean
"Fenchurch is correct, as usual."
- muscle23ftl