Argument from authority to some extent is a necessity, you always have to find some common ground from where you can make your deductions. If you push it far enough you end up with
cogito ergo sum sort of things and
Gödel famously showed that even mathematicians need to take some things on faith, etc.
It is considered too cumbersome/difficult/time consuming to deduce even the "elementary" math we teach in schools from the axioms, so we rely on the authority of books and teachers (and "common sense"). In other subjects it just gets harder. To provide some fairly conclusive evidence for the existence of the Higgs Boson you need a 9 billion USD accelerator to begin with. Most of us, even physicist, will just have to trust the experts when they say they found it.
If your uncle is saying the theory of relativity is a scam, do you trust him or the majority of physicists saying otherwise? I suppose you try and convince yourself by making different experiments (inevitably based on a lot of assumptions you have learned from other authoritative sources), but it is simply to cumbersome and time consuming for most.
We are all forced to take most of what we know on faith from different authorities. It's the only rational and practical approach ("informal logic"). (Although that doesn't mean that they are always right). I think we should be more up front with this unfortunate reality and schools ought spend more time trying to convince people
why they should believe what they are being taught (
scientific method) at the expense of some of the facts they will have forgotten the next year anyway.
I believe conspiracy theories sometimes come from loosing faith in these authorities, if you start pulling the treads the things we think we know start to unravel. If you don't see a reason why you should believe what your teacher told you about evolution (
i.e. the scientific method) but rather just see it as gospel from a preacher, then there is really no reason why you couldn't replace that preacher with another who teaches creationism, or something even less orthodox in another church in the future.
So, yes, while there certainly is a time and place for formal logic and the study of fallacies and such, it makes little or no sense to solely rely on it in informal discussion between laymen.
I do think it is useful to
recognise many common fallacies though. Call me paranoid but I too often get the disturbing feeling that quite a few people use fallacies deliberately, in a very Machiavellian way, to spread disinformation and derail debate that isn't going in their desired direction. But that just makes it even more counterproductive to follow their bait down the rabbit hole, it just takes attention further away from the core issue.