The problem is that there aren't a whole lot of new movie theaters being constructed any more, certainly not any large enough to host a full size 70mm IMAX screen (which is significantly larger than the screens used for 4k digital).

Regal and AMC absorbed or drove out all the smaller companies, and the margins aren't good enough for new companies to enter the market. You need a dozen screens to diversify against poor performing films. A dozen projectors is a pretty significant cost investment for a new company. That was the case before COVID decimated the industry, and now its even worse.