You can tell if you see the person is arrogant. If they are arrogant, they receive their Torah lessons and ideas from the side of the demons.
This seems to me to be very relevant nowadays that there are very few teachers of Torah who are not arrogant. At least that is among the teachers of "hashkafa [frum world views]."
Arrogance is in manner, but it also refers to thinking one knows a subject without the proper preparation. World view issues have the odd trait that people without knowing much about Torah can have opinions about Torah issues.
So you don't get many frauds being Math professors. This is the same reason you don't get many frauds in those that teach Gemara, Rashi, and Tosphot. The subject is inherently hard. But world view issues of Torah is different in that people can fake it easily. [It is easy to pretend that kabalah is hard and to pretend to know it. It is hard to pretend the same kind of thing with Math or Physics. The subject matter itself weeds out the phonies, and then they go to yeshiva to pretend to be smart.]
The problem is there are too many fake yeshivas. Now some people ought to be sitting and learning Torah that is Gemara, Rashi, Tosphot. But most can't. It is too hard. But they can't work either. They have no skills. So you get fake yeshivas where people are not learning Torah but pseudo Torah.
The truth be told very few people after the age of eighteen should be learning anything at all. Not Torah and not humanities. They should be flipping hamburgers. Maybe 5% of the people that can be doing STEM or Torah should be. But I know of very few people like that. The rest of the garbage they are teaching is not worth it for the people learning it teaching it or supporting it.