To be fair, "nothing happening" can equally well describe much of the Western post-modern literary tradition.

I think one thing that sets Murakami apart is the earnest simplicity of his writing. His writing seemingly doesn't attempt to manipulate the reader, and it doesn't seem to aim beyond high school English in complexity. It's workmanlike, unaffected, and personal. To me, it brings to mind John Williams (Stoner) and Karl Ove Knausgaard (who is admittedly a much more capable prose stylist).

In his earlier works, the simplicity feels a bit... simple. But in hi later, more mature works, he doesn't shy away from going into detail about the sheer mundaneness of living. I haven't read 1Q84, but the first book to really deserve the stereotype of Murakami as being about single guys with cats lounging about in empty apartments while waiting for the pasta to boil is The Wind-Up Bird Chronicle, the core theme of which is figuring out reality, and by the extension, life. It's a work where the economy of style meets an economy of plot (even though it's actually a complex plot!) perfectly, and it's a masterpiece.

I've never been to Japan, but I find his other concerns you mention — isolation and so on — to be just as relevant in other social-democratic cultures (perhaps the US less so).