Who wants to see a movie about Krypton being destroyed? The amount of time spent on it in the first Superman film was more than enough. Not even close to enough people are going to want to go see a Superman movie where a bunch of intellectual aliens are waiting around for Krypton to be destroyed.
See, you're making the mistake of assuming that the way Donner portrayed Krypton is the only way of doing it. Have you ever seen the first episode of Superman: The Animated Series
? It focuses entirely on Jor-El and Krypton, and it's an action-packed thriller all the way. The portrayal of Kryptonians as cold intellectuals is pretty much limited to the Donner movie, the John Byrne comics reboot, and their imitators. The Krypton of the Silver Age comics was a far livelier, more human place, as was the Krypton of S:TAS.
And really, Jor-El's story fits the classic template for a disaster movie: a lone, crusading scientist tries in vain to convince the hidebound establishment to listen to his warnings, he's proven tragically right when the disaster strikes, and then he takes the lead in dealing with the consequences and trying to preserve some survivors. It's only at the ending where it diverges from that template, because usually in a disaster movie there are more survivors than a single baby.