There's no such thing as "bad aspec rep"
Well, there is, but the bar to call a single character in isolation bad aspec representation is extremely high. They would have to explicitly look into the camera and say something like: "I am evil and a bad person because being aspec is inherently evil and bad" in full sincerity and with no trace of internalized aphobia and the narrative treat this as if it were correct. And that's something I've never seen.
Because otherwise, even if you don't personally relate to the way a character is portrayed in that media, someone does. And whoever does relate to that character deserves to feel seen and represented.
Obviously, metatextual conversations of how characters who are aspec are treated and discussed outside the media can and should be had. But one thing that should never be said is "The way the character is shown in the original media in isolation is inherently bad."
I don't care if you think they're a stereotype.
I don't care if you think they are a bad person.
I don't care if you think they are heartless.
The issue with aspec representation in media is not a burden to bear for any individual character. If you treat every character as needing to represent the entire spectrum, they will always, always fail. This is a much larger issue that can only be solved by there being more, varied aspec representation in general. And bashing creators for "bad representation" just because it doesn't reflect your personal experience only scares people away from trying to handle aspec identities. If you want a certain type of aspec representation, create it! And encourage others to do the same. Don't harass people for representing another part of the aspec just because it's not yours!
I'm going to use Alastor from Hazbin Hotel as an example, as well as Mammon from Helluva Boss, because this is a universe with three different canonically asexual characters, and the two whose identities we know anything about are treated very differently, both in the show and by the audience. (Via we don't know much about her identity, so I won't be discussing her as much).
Alastor is a coded as a touch-averse, romance-averse, and sex-averse, nonpartnering, bold-stripe aroace. Mammon is coded as a sex-favorable alloace or a sex-favorable and romance-favorable aroace. Those are two very different types of aspecs, which is great! We need more media that acknowledges different types of aspecs.
And yet, Alastor constantly falls under fire for being "bad rep." Why? Well, I've seen him called heartless, emotionless, robotic, and a stereotype. Specifically because he is coded as a touch-averse, romance-averse, and sex-averse nonpartnering, bold-stripe aroace. Um, guys, people who are actually like that exist. I'm one of them (I'm not touch-averse and sometimes I feel more like I'm rose-repulsed than averse, but I might be okay with a QPR someday with my best friend) but I feel incredibly seen and represented by Alastor.
It's fine if you don't, but instead of calling him bad rep and catching people in the crossfire, maybe critique how the meta and the fandom treat him, rather than how he is in the show itself? Maybe don't imply that bold-stripe aroaces are heartless or robotic? Maybe don't call nonpartnering aspecs emotionless or a "bad stereotype".
And if you want a sex-favorable ace character, there is already one in the same universe! Now, of course, you can play around in the sandbox of fanon a good bit, but I'm exhausted of people calling Alastor bad representation in the source material when I have never felt more represented by a character before. He's not just aroace-coded, there's a lot of things about him that are femme-coded or autistic-coded (like his smile), and that's really awesome! Also, he has a lot more emotional depth than people like to pretend. He's not some flat, evil caricature, and the fact that so many people call him that while critiquing his portrayal as an (aro)ace character rings some alarm bells for me.
Again, you can critique how a character is treated by creators and fandom without just blanketly calling the character bad representation. Whether or not it represents you, it represents someone, and that someone deserves representation as well. We need more and varied aspec representation, and the only way to get that is to celebrate aspec characters instead of constantly bashing them.
Edit: "rose" simply means "romance + sex". When i say I am "rose averse" it means that I am both romance averse and sex averse. "Bold stripe" refers to an aroace who experiences absolutely 0 romantic or sexual attraction.