A big problem with fallacy lists is that they aren't sensitive to context and don't even make an attempt to investigate what supposedly makes something fallacious in the first instance.

Ad hominem is probably one of the best known fallacies. But personal attacks aren't always fallacious.

For instance, sometimes we have to make judgments based on credibility. That happens quite frequently. And, sometimes, it's impossible to do anything else.

Imagine you're on a jury in a medical device defect case, and you don't have any knowledge about the subject matter.

Each side presents its experts. The plaintiff's expert is a well respected expert in the field. The defense's expert is what some in the law might call a whore. He'll say anything you need him to, for the right price.

In closing argument, the plaintiff's lawyer argues that you should decide in the plaintiff's favor because their well respected expert is more credible than the defense's hired gun.

That's an ad hominem argument, but it is not fallacious. You have to decide whether to believe someone, and their past conduct and reputation are relevant to that decision.

The defense expert's history and reputation don't necessarily make his statements false in this case. And maybe the plaintiff's lawyer was bought off for the first time.

But their respective personal characteristics are proper considerations, which means it is not fallacious to make arguments based on those characteristics.

That might not be true when some mathematicians are making arguments about the validity of a proof. In that case, the ad hominem is not a proper consideration.

If you use fallacy lists more like mental checklists of things to watch out for, you'll be in good shape. If you use them reflexively reject arguments, you'll be making a mistake.