It’s interesting that you bring up Aliens because it’s a great example of how a character with previous history can fill a new role effectively, exploring different themes than in previous installments of a story.

But it also highlights the need for major changes - Ripley is the only carryover from Alien, and her character wasn’t really fully fleshed out in the first movie, so they had room for her to be whatever they needed her to be in a follow-up. She’s not a bad character at all, but she doesn’t need a whole character arc to fulfil her role. That’s not the case with most TV series because having thin protagonists at the end of a season generally doesn’t make for compelling or satisfying TV.

Aliens also works because they introduce new elements to the horror - the thought that there’s an intelligence directing the Xenomorphs is terrifying, and the threat it poses to life on earth is almost cosmic horror in its scope. You see that Stranger Things tried to take the same tack, but it was bogged down by its own lore and the limitations and having to work with a whole cast of characters who are experienced in fighting this very threat.