It took me literal years to figure out the appeal of Jazz/Prowl, and after reading this, I strongly suspect that the fandom approach to Jazz was part of the problem. Prowl was the one I got attached to, and I write him as autistic and prone to crashes when faced with the unexpected (in no small part because I got tired of people using him passing out as a comedy beat, but also because hey! Quasi-canon disability!), so I approached the pairing from that perspective. And Jazz just struck me as too unpredictable to be a good partner for him (also, I'm not a fan of extroverted characters "fixing" introverted characters by making them get out more, which is a fairly common trope with extrovert/introvert pairings in general).
Of course, I'm a canon-centric writer, so the first time I sit down to write something from Jazz's perspective, I'm left realizing that he's... Not that? Yeah, he's more spontaneous and extroverted than Prowl, but he's also capable of accommodating for a partner? Like... He's chill. He can be comfortable at a party or spending a quiet evening at home. And he's also a freaking adult, he can have conversations about boundaries and negotiate compromises and stuff.
I also tend to mostly reference from the pilot when I write G1 Jazz (y'know, because the rest of the series kind of dropped him actually acting as an officer), so it frustrates me when he's written as hating or avoiding paperwork in favor of having fun. All of the G1 Autobots are more laid-back and immature than is realistic for their circumstances (it's a side effect of being heroes in an 80s children's cartoon), and Jazz is near the top of the Autobot food chain. You can't tell me he's incapable of being serious and doing the boring parts of leadership.
That being said, I have written Jazz as an antagonist before (he's not special in that regard. Other villains in my roster of unposted WIPs include G1 Optimus and Soundwave, neither of whom are normally written as villains). But like... I don't like Sadistic Assassin!Jazz. I write him the same way as an antagonist as I do when he's a protagonist, he's just less friendly if you're a Decepticon. A lot less friendly.
(Also, since the original ask mentions him being written as a nymphomaniac, I feel like it bears mentioning that my Jazz is on the ace spectrum. Likes to watch and to take care of a partner, but not always interested in participating beyond that. This was not an intentional match for Prowl, whom I also write as ace, but it does simplify their sex life. Which does exist, they still have attraction and libido between them. Just not both in the same bot. Because I like writing about different kinds of asexual experiences).
Anyway.
TL;DR: I like my Jazz better than fanon Jazz.
While I mostly talk about issues like bigotry, cases like this where people don't even realize a thing is all a lie fanon and it causes them to not explore a character who's really great for ages is also a major reason I make posts pointing trends like this out. Since I'm a big Jazz fan, if it's okay I'd like to discuss some more canon Jazz facts that might interest people and really relate to what you've said here! I have so many more links about Jazz I can share too lol
Keep reading
If most of the "Jazz lore" is in the Marvel comics, I would have to say I'm not surprised no one talks about it. Most people don't talk about the Marvel comics, and I have no interest in reading them myself (I did skim through a few issues. I didn't enjoy it).
As you seem to mostly be coming at Jazz from a Marvel perspective and my only exposure to the character has been the G1 cartoon and a few IDW comics, I shall refrain from commenting further.
I hated the US Marvel comic so, so much. From the art to the writing to… everything about it, really! (Except for the letters section. That became my main reason for picking it up, because I ‘met’ most of my TF penpals that way.) However, reading this conversation has made me realize that I probably hated it because I’m a Decepticon fan, and a Starscream fan in particular, and that an Autobot fan reading it would probably have had a very different, far more positive, experience. Which is kind of instructive. We may all be reading/watching the same stuff, but we’re not all (necessarily) having the same experience. “Same planet, different worlds,” as they say. (Apropos to nothing by the way, just something that struck me.)