National Amusements wasn't considered an official breach of the Paramount decree because it was "the other around", a theater chain owning a studio rather than a studio owning the theaters. It also got a lot of weird exceptions because National Amusements was entirely private at the time.

But the current issue is right now streaming services dwarf theaters today. The Paramount decree was officially suspended by this administration and its courts on this matter stating it isn't a monopolistic oversight for studios to own and entirely control their streaming services (despite doing the exact same things with "originals" and "exclusives" that led to the original Paramount decree). This administration and its courts not only said the current streaming situation is fine, but that it also means the original Paramount decree no longer applies and studios may own theater chains again, because theaters now compete with streaming.

Skydance having both Paramount+ and HBO Max gives them a huge amount of leverage in the streaming space that is going to get stranger with this consolidation, and gets back to why that 200+ years of combined film history is important and relevant.