In my defence, I just don't care

It's probably a bad sign when I laugh at the introduction of every character on a show, be it hunky white boys with impossible hairstyles that retain that stiff, erect and proud profile no matter what gymnastics are undertaken by their stunt doubles, or laconic, complicated black guys who smolder their way through the scene of a homicide while explaining to their captain - who looks like she's twenty and a model - that women cannot understand him and he can never be close to them.  Then a geeky spectacles-wearing dude is introduced as the "best friend" of the hot redhead (black eyebrows) lead character and really, at that point you're not waiting to see how this relationship unfolds, you're just waiting to see how the show explains to you that he has the hots for her but it is not reciprocated because you have seen this in every other show and you are getting it now, too.  She says "how can you not notice that someone so close to you has the hots for you?" and the guy strokes his chin and looks her in the eye and says "HOW INDEED" okay maybe that is not exactly how it plays out but believe me, I am not paraphrasing things quite as much as you may suspect.
Also, in a show that is clearly populated by twenty-somethings (and their thirty-something parents), much is made of the fact that the lead character is just turning 18 (an actual line from the character: "I'm turning 18, it's not like I'm setting off on some epic journey"), which for some reason struck me as odd that the forces of evil and magic in general would have the age requirement for giving legal consent to sexual intercourse in North America as their barometer of whether someone had "come of age" or not.  There's actually a deep and rich mythology surrounding the ascent to womanhood in magical cultures... I'm sure some of that will come up in the course of later episodes.
"Sorry I'm late, the captain has got me on those demonic murders" "literally my brain is about to explode!" - actual lines of dialogue from this show, FYI.
This all might give the impression that Shadowhunters is some kind of metatextual hoot at the very least, but that would be a misleading impression to give you as such a thing would require a level of self-awareness the show doesn't have.  Shadowhunters is not self-aware - if it was, at some point a character would stop and announce "the world I am in is a load of turgid shit" - no, Shadowhunters is just shit.  Shit that I honestly believe has had creative input from 12 year old girls, because it is like something my niece would create during that strange period where she stopped drawing her graphic novel opus Poo Robots and started saying "I like Gerard Way's music" unironically while plastering her bedroom wall with pictures of hairless androgynes she insisted had deep creative insights to impart to the culture.
I mean, don't get me wrong, I'm not being hostile towards Shadowhunters here, I totally understand there are many demands placed upon a creative  production from various quarters over a relatively short space of time.  Buffy was a great show in its day, but there's no law or anything that says that a show has to have a coherent creative vision and tangible purpose or themes, that was just something Joss Whedon brought to the table after years of honing his craft and learning to work within the demands and confines of television production to deliver the best possible product - it's unfair to expect the same dedication to storytelling and the inherent belief that the audience is not composed of drooling simpletons of a modern production team who construct their narratives purely by stringing scenes from other tv shows and films together and who maybe get genuine input from the higher-ups a few times a day along the lines of "more twenty-something models taking their shirts off" or "less talk" or "something from the Billboard charts from a month ago" or "he talks for a long time in this scene, can he have his shirt off?"  The demands of television are different now than they were in the late 1990s when kids could pay attention for 40 minutes, as now kids have one eye on their phones while they're watching stuff, so they probably won't notice your clever use of sound or your inventive nonlinear plot structure or your subtle character study, so you're better off if a song they might like suddenly plays or someone takes their shirt off as that way there's a good chance you'll get their attention away from the Twitter and the Instagrams for a minute - of course, if you've abandoned all pretense of substance as Shadowhunters does quite early in proceedings, there's the obvious question of what they're actually going to see when they do look away from the Twitter and the Instagrams for a moment and what great insight or original turn you have to offer, but there's probably a good chance they're on the Twitter and the Instagrams in the first place because they're a moron, so all they need is the music and the shirt coming off and you can call it a day knowing you did your best as a creative entity and your audience likely got the show they deserved - the dumb fuckers.
Strange but true: like Buffy, Shadowhunters is based on a movie that did a major belly-flop in cinemas, and I recall this only because I thought it was funny that I couldn't even make it to the end of the trailer, never mind watching the actual film.  I made it to the end of the first episode of Shadowhunters, though, and if you don't fancy your chances of doing the same, someone has handily done a supercut of all the plot scenes of the episode on Youtube that clocks in at just over 19 minutes - for some reason they've animated it, made it in 1998 and called it Invasion America, but trust me, apart from a gender-swapped lead character it's the exact same fucking story.