The narrator of the Murakami novel is relatively passive. He reacts to things but is not the main driver of events. Menshiki is the instigator of most of the action, having the nameless narrator paint his portrait and then the portrait of the girl who may or may not be Menshiki's daughter.
The common wisdom is that a protagonist should want something, and take action to achieve it, and then deal with the obstacles that arise. Here we don't know what he really wants. His wife has left him, and he has affairs with some women, but they are not what he wants, really. He perhaps wants to forge his own artistic style, rather than being a painter of commissioned portraits, but to do so accepts Menshiki's commissions. It is Menshiki's money that permits everything to happen.
A passive protagonist can work, but it is much more difficult to pull off. It doesn't feel satisfying, so something else must compensate. Verbal descriptions of someone painting are not wholly satisfying either. There is something half-hearted about the whole novel. as though the author didn't know what he wanted to do in writing it.