Yes, but these are likely coming loose due to vibrations over many flights. Other airlines did an inspection after this news broke and found similar problems. Alaska was just the first to run into issues from it.
IIRC Alaska Airlines knew the plane had issues and decided to keep flying it anyway.
So yes, it's Boeing's fault the plane's door blew off, but Alaska Airlines also deserves blame for continuing to fly a plane that was reporting issues with the door hatch.