I too find the new themes (other than Rey’s which is rather like something out of John Ford Western) a bit uninspired.
All the films 1-6 had memorable themes you could hum or whistle after leaving the cinema.
I didn’t have one this time.
You’re probably right on immediate hummability, but for me that’s not the barometer of a good score. For me a good score has themes that develop and intertwine throughout the film and support what’s on screen. There’s a coherence and sophistication to the music in TFA that hasn’t been there in a SW score since, I would argue, 1980.
And I found the themes quite hummable after a couple good listens to the soundtrack.