Hell, every aircraft is slightly different and the pilots and/or service people don't treat them as such (although in practice typically the differences may be negligible for the pilots -- but they will check).
So based on that it is absolutely the airline's responsibility to make sure that the people operating any equipment are checked out on it.
So it is possible (though pretty unlikely) that Boeing failed to follow their protocol, e.g. didn't send out the right notices on a timely bases or something, and if so they would be responsible. But with all the airframes they've shipped over the decades that's pretty unlikely.
From what I have been reading in other articles (sources available if you wish), most of the comments from folks in the industry have been that Boeing DIDN'T give the normal, proper notice to airlines. The prevailing sentiment is that most everyone was caught relatively unaware that this feature had been shipped on the new airframe. Mind you this is mostly hearsay from mainstream media, so I am taking this with a grain of salt. Oversights tend to get sensationalized.
I understand that it probably SHOULD have been read, but I'd imagine that a line about this particular scenario could easily be overlooked even if one did review the emergency procedures for the MAX aircraft before piloting it. That is still a pretty flimsy excuse even if there is a grain of truth. This isn't some Monday detail that will cause a redeploy next week. A large number of people are dead as a result of this accident.
How a system that can so stubbornly keep overriding manual input made it onto a modern aircraft is concerning. I will admit that I am not in the industry and am speaking from a platform of ignorance, but it's less than comforting knowing that I may go up in a plane with such technology in place.