I said prior to release that the film was set up for success from a scheduling & marketing stand point. I still believe that. Unfortunately, general audiences simply weren't interested, or so it would seem. A 71% decline is atrocious, made even worse by the fact that it's Memorial Day weekend.
I don't know if a Ripley fronted Alien 5 would perform any better. Nostalgia is in, but it's hit or miss. Jurassic World cleaned up whereas Independence Day Resurgence was largely ignored. Of course, quality may play a factor. I'm someone who is open to such a film happening, even though I adore Alien 3.
Why does this franchise need a reboot? What constitutes a reboot in your eyes? Resurrection, though a direct sequel to Alien 3, surely sought to renew fan interest in the franchise. Prometheus, while a prequel, once again attempt to bring audiences back into that world. If by reboot you mean remake however, then that's something I don't have any interest in.
I don't know what would pull in new, or old, audiences at this juncture. I found Covenant disappointing. No, it's not the worst film in the franchise given there's still Alien Resurrection, but I'd rank it behind everything else.