And there's the rub. Lingo isn't inherently evil, in fact it's necessary to get through day-to-day life. You can't refer to every tool you use on the job with a short sentence explaining what it is, you say it's name and the people you work with know what you're talking about. The only time lingo must be avoided is when talking about something you're familiar with with someone who isn't to avoid putting them off or confusing them.
The real danger is people not realizing how (contrived, constantly changing) lingo can be used to manipulate them, specifically how it drives tribalism and the "us versus them" mentality. This is especially important given how political movements and other groups behave online, and how prevalent this tactic has become over the past decade.
Yes, "on point" is slang, but only just recently. Slag is just a little further down the scale in terms of specialized language.
The real test is how accepted a word or phrase is with the larger population using a given language (while keeping a specific meaning in mind). This gets a little muddied with the lingo used by larger groups.
For instance the phrases "weird" and "cat lady" have both been co-opted by the major political parties in this election to decide their opponents. Because they each have so many members and because their discourse is covered by media outlets the new connotations of those phrases will be more widely known outside of the group and will stop being lingo much faster than the phrases you use privately with your family or coworkers.
"On point" used to be lingo in the military once upon a time, but because of the size of the military (and aided by the internet) it has become slang and is no longer a phrase only used by a certain group.