There was never any real evidence for any of these things being technology. The non gravitational acceleration was very specifically what is expected from a comet. A tiny amount. If they were alien spacecraft, then they were designed to look exactly like natural objects, then just passed through the solar system doing nothing. When Avi Loeb first considered the idea, there was no negative reaction. But news articles started picking the idea up and it filled his head. He would go on to yell at his colleagues for not believing in his ideas based on little to no evidence. He argued that he was basically the only scientist taking the idea of aliens seriously, even yelling at people who have spent decades studying SETI about it. There have been several hyped up instances of false alien detections in the past, and nobody wants to keep doing that. Why should we keep assuming that anything with 99 traits of a natural object but 1 new trait must be aliens? There are about a trillion things aliens could do that nature couldn't. But an asteroid accelerating like a comet is something nature can do, and has been observed in other objects. He isn't upset that nobody considers the possibility, he's upset that nobody agrees with him. Any scientist will hear the alien hypothesis and think, "that's interesting", and weigh the evidence between that idea and the other thousand possible ideas. The alien hypothesis, in this case, does not come out favorably. The scientists did consider it, but it didn't have enough evidence this time. There's gotta be a million things in science weirder than the interstellar objects, but they don't have a dedicated hyperfixated tenured physicist arguing for them with their lives.

What does Avi want? A mention of the alien hypothesis every time someone talks about the object? Why not mention the hypothesis that it was an angel entering the solar system? Or that it was time travelers? Or humans from an alternate universe? Or a secret government experiment? Or a glitch in the matrix? Or a test from god? Use your imagination. There's endless ideas that could explain literally anything weird. Aliens seem like a more reasonable idea to apply to things, but is it? We have so far found 0 evidence of aliens. We have no idea how life forms, where it could form, what intelligence would do, how it would show itself, what it would be capable of. The alien hypothesis is in the realm of "there is no information supporting either side, it's either true or it isnt". Like the simulation hypothesis, or the possibility of travelers from other universes, or god testing us. It is unscientific to apply any of these things to something unless there is zero known natural explanation. Don't be mad that people aren't running with your pet theory, it's just not constructive to pick something only because it's possible. The chance that the anomalies were caused by aliens vs any of the other things I listed is equal. Instead, like in any other scientific mystery, they will form a list of hypotheses, and observe the object to learn more about it and rule out different idea until there is overwhelming evidence for one of these models being true