I don't think it is fair or helps anyone to make assumptions.
You assume it isn't hard to update the engine, do you develop in Unreal Engine and could shed some light on it for us?
You assume it is only Gizmo on the development team, have you asked, or have been told who was developing on the team?
Sometimes it is very difficult to migrate to a higher version of software, and some things may be easy.
Gizmo may have 10 Devs working on this game, but to assume it is just him is silly.
Sometimes when new software comes out, it breaks the previous version. This is very common in software development.
For an example, when windows 10 was first released there were a lot of drivers that would not work with win 10 because of the new software, and that is only 1 version difference.
Everyone should be thrilled of the new stuff coming up, I know I am, but it may take some time.
So let's demonstrate some patience peeps.