B737s are quite run down, and the overhead bins are made of the kind of plastic that makes this painfully visible (at least for pax that are tall enough to see this).
The seats i normally find OK, but they do not have this newness polish that LH is good at. I guess this is entirely Scandinavian. Things have to be good, not necessarily brand new.
But I have not seen excessive dirt, etc. recently. I fly CRJ routes a lot, and I think these machines are still relatively new and clean.