Mallomar SF has a superficial shell of crunchy hard science, but when you bite into it’s full of fluffy, gooey magical science and bad science.
Take Heinlein’s The Moon Is a Harsh Mistress, which I loved when I was twelve. Heinlein lovingly calculates the kinetic energy of the lunar bombardment, while completely omitting the amount of energy lost as the projectiles go through the atmosphere. Or the glaringly obvious heat signature of the second catapult’s radiator.
Or the economic absurdity of growing wheat in lunar caves with fossil ice for export to Earth. That’s pretty silly even before the ice starts running out.
Given the presumption of competitive fusion power, that would would be hopelessly more expensive than, for example, growing wheat underneath Antartica.