There are numerous YouTube channels where people are claiming to debunk what they call ''so-called body language experts'' saying that it's all bullshit etc, but the reality is as I've mentioned here, although there are tons of snake oil salesman so to speak online, the study of human behavior and non-verbal communication is an interesting one, and a legitimate one. It stands to reason, considering the majority of human history we've communicated non-verbally or at the very least without words like we have today. You only need look at the rest of the animal kingdom to see this.
Body language interpretation does have some key points to note:
There are no absolutes in body language, first you must establish a baseline behavior in the subject being assessed, then look for deviations from that, and you're looking for clusters of behavior as opposed to just a single behavior. no one piece of behavior is indicative of deception for instance.
There are some very good reputable body-language channels on YouTube so it's a shame to assume they're all bullshit when they're not. If you always base all of your beliefs on evidence, and think critically, you can't go wrong.