It is not the only way to judge the quality of a book, but it is certainly one of them. People talk about how comics are a dying industry. Perhaps the publishers should question why since the 1980s many comic cost at least three times more for half as much.
And clearly comic with more beats per page are not neccessarily extrordinarily bad or unreadable, since the industry have survived to this point with a long history of such publications. Some of which, like the Dark Phoenix saga, are now considered classics of the genre.
As an example...
If this page were written and drawn now, it would have taken at least three pages. After all, there is no way modern writers would let that final blast go by with anything less than a full page splash, maybe even a double. The dialogue before and after would have been spread over seperate pages either side.
Thing is, you have just cut into two pages of the book and the other pages have their own emotional beats that would demand expanded telling - the battle between Colossus and Gladiator for example, and Jean and Scotts last stand. By the time moders creative teams were done the book would have stretched out over four issues [it was already double sized, after all] and might still have bits trimmed.
Would having the page above expanded like that have made the story better? I personally dont think so.