IMHO, the only reasons for using 70 mm IMAX are nostalgia and marketing. Digital movie cameras have far better color reproduction, more dynamic range, zero frame jitter, and plenty of resolution without grain. They are also small and silent which allows far more interesting shots than what is possible with a 70 mm monster. Kubrick and Lean used 70 mm because it was the best technology available at the time. Today, the best technology is digital.
I agree, I actually saw specks when viewing the Odyssee on 70mm IMAX. Sorry, but how is that "better" than any clean, digital projection? And the hoops they apparently jump through to make it work during the shoot to get to that point. Pure nostalgia hysteria.
Digital cinema projectors are mostly stuck to narrow colour spaces so most often than not people will have better colours on film projections rather than digital. Same thing for dynamic range. Keep in mind that DCP standards have really not been updated since like 2010.
I'd say one of the advantages of analog filming is it's more expensive to "color correct" digitally after. So maybe you get less monochrome films?
I think it's misguided to say things like "IMAX 70 mm has an equivalent of 18k resolution." But have you seen a 70 mm IMAX projection? In my experience, the 70 mm image looks noticeably sharper than an equivalent 4K digital IMAX projection.
1.43 IMAX 4K is also a great experience, but its resolution is a meaningful and noticeable limitation given its massive angular image size. It's a compromise compared to a more traditional 4K cinema screen (like a typical Dolby Cinema screen): with IMAX 4k you gain angular image size and lose "pixels per degree of visual angle." And both are noticeable!
I agree with you that the latter has all the advantages you listed, but there is still something truly special about the apparent resolution of IMAX 70 mm projection.