No, Starship Troopers was not a direct endorsement of fascism. This is exactly why it wasn't a good adaptation, largely because Verhoeven famously didn't even read the very short novel he wanted to criticize but he's convinced a horde of fans of trash movies that the novel says things it simply does not.

The movie made up the majority of its criticisms of Heinlein's fictional society, including misrepresenting the process of "earning" citizenship, the most suspiciously fascistic element that in the novel is much more benign, and throwing out a completely fabricated plot hint that Buenos Aires was a false flag, as well as portraying the Pseudo-Arachnids as simple space bugs when they're a technological species, but he didn't bother critiqueing all the time he spent on malding on modern military officers being hyper-responsible warrior-poets.

And that's, like, the bad part! Which he'd have fuckin known, if he'd read the fuckin book!

Heinlein is best described as a militarist liberal, and eventually a neoliberal when that became a thing. He literally ran for office as a Democrat in the Reagan years.