If they brought back Alien Encounter as a quick fix none of the seasonal problems would happen. It fits in the Magic Kingdom because the attraction uses magical technology to experience the alien crawling all over you.
Nobody should care if it is too scary. You're at a theme park , not a grocery store. Not everything should be expected, or else it's pointless.
So, you say "nobody should care if it is too scary". Well, I never thought in my life I would say this without irony: "Will no one think of the children?!"
Alien was too scary for children. And that's in the one out of four parks most specifically designed to be 'family friendly.' Heck, Stitch is going away because he was too scary for children, so, Alien was worse.
So, too scary is a concern for enough people that Disney is finally shutting it down.
And even if the old Alien AA is still around, Disney ain't going to pay to put it back only to demo it again with the next ride is ready. That's throwing money away.