Maybe its because of trends in screenwriting? In Alien and Aliens nothing action packed happens for ages (I guess SM can say when the inciting incidents are and all that stuff), but for maybe half-an-hour, its just the Nostromo crew talking and arguing or Ripley having as shit time from the company.
Predator I'll grant you is a little different, but in the cases of both franchises, the characters are great - cliched now, but then not so much. You know who these people are and you care about them. And there's heaps of tension built in (even if its as Honest Trailers points out, people quietly looking at trees).
Is it the case that writers these days are following the beats and that means that shit has to happen and fast? So as Sentry Gun, suspense et al are being replaced with spectacle.
I've not seen "The Predator" yet (I should go tonight, actually) - I can't speak for that one. BUT, I will defend "Predators" - OK, it was very (very) similar to the first one (very very very similar. A virtual remake in fact) but again, the characters were good.
They WEREN'T (in my view) carbon copies of Dutch's squad, the alien setting was good and I think the only real mis-step was the inclusion of Fishburne's character. I liked the idea, but I thought that whilst he's a brilliant actor (he is) he was physically not right for that role.
I liked the bleak ending, I liked that Royce was morally ambiguous (he had an arc!), I liked that Topher Grace was how he was. And again, that one took some time to get going. And parachute opening sequence was ace.