> I guess, it was an okay movie, but hardly the cult classic everyone keeps talking about,

But it is exactly the cult movie that everybody keeps talking about. Maybe it wasn't a blockbuster because of the reasons you give, but it had an iconic look that has influenced every SciFi movie since, and it takes its time to tell an interesting, complex story, where you can't really be sure who the good and bad guys really are.

It's popular exactly because it's different. It was and still is immensely influential. But it's absolutely true that it's not standard middle-of-the-road blockbuster material.