The trilogy - Alien, Aliens, Alien3 - is thematically and conceptually coherent. The fourth movie is an extension that is not without some merits and puts a clone of Ripley "beyond" what had been done (after confronting the monster, then the monsters, having the monster inside her, this clone of Ripley was the monster and had a strange relationship with the aliens). It has a different spirit (with a focus on humour noir and irony).
An alternate history about Ripley and co. after Aliens is not an heretical idea for me. It could be interesting, if well made. But I found the original end of the character very satisfying. If Alien Covenant is more satisfying than Prometheus, I'll without a doubt prefer a continuation to that trend, rather than a reboot of Ripley's story. I write that while thinking that of course seing Sigourney Weaver in another Alien movie would be cool. But I won't be mad if it is not done.