Some interesting comments. I still believe that many are overestimating the so-called "word of mouth" for average cinemagoers.
War for the Planet of the Apes was considered by some to have underperformed akin to Alien: Covenant. Like Covenant, some erroneously have called it a flop (it really isn't) but certainly there were hopes for higher box office totals. However, it received great reviews, has a 93% on Rotten Tomatoes, and is being bandied about as a potential Academy Award contender for Best Picture.
So, "word-of-mouth" has limits. If it was a major indicator for success, "War" would've done better.
At the end of the day, there is no 100% accurate scientific metric. The reality is that what FOX interprets from the numbers is more important than what you, I, or anyone else determines to be the "truth." FOX seems to be moving away from the "Alien" brand as a result - Scott's comments are reminiscent of those while Prometheus was in development.
The "just make a better film and people will see it" is not realistic. If it was, then why are so many Academy Award winners for Best Picture not hits and many in the public are unfamiliar with the titles?
I conduct mini-surveys with my students and when asked about this issue, most say they don't base their opinion on Rotten Tomatoes or some other aggregator. It's not a scientific survey - but noteworthy. Interestingly, most of these students (18-22 years) have never heard or seen any Alien film. And that my friends is perhaps the greater issue . . .