I disagree. Have you ever been to a real 70mm IMAX screening? I don't mean your typical "IMAX". There's only a handful in the whole world.
The quality is gorgeous, and the screens are huge. You also get significantly more of the frame than you will in traditional cinema and on bluray releases.
Don't call it unnecessary until you've actually seen it. Digital IMAX isn't close yet.
The reason it's unnecessary is that digital can completely capture a 70mm in high enough resolution that you perceive no difference at all. 8 or 16K projection is completely feasible in commercial projection systems. It means the cinema only has to deal with a small box instead of an enormous roll of film.
That doesn't mean either digital IMAX since that's old tech using something like 2K projection which isn't adequate.