Dirk in his longing to survive and understand his inner and outer world latches on to depersonalizing his living experience. There's also the added bonus that in his current world socialization happens only through internet and he has no social paradigm at all, to him all the tools he has to understand life, how to live and all the jazz that comes from having a smarter(but more depressive) monkey brain is thought logic and machination, which is funny considering his denizen is Yaldabaoth i.e. the trapping of the soul in the material, double funny if you take Roxy's void aspect, and specifically as a thief of void, as Sophia.
Dichotomously Roxy seems more present in their lived experience, though she is at the beginning continuously dazed (an expression of the void element when she lets themself be influenced by it and not embody by itself) once she is more active in her choices and in living its aspect he lets himself be freer in the experiences, learns through doing and therefore her knowledge comes from being a spontaneous presence in the world. This is why I believe Dirk is so enamoured by her, to him, that everything needs to be catalogued and every interaction planned so that he can react and function in the world without losing his shit. Roxy's spontaneity and willingness to be there, in a conscious emotional state seems impossible to recreate. In fact, he holds him in extremely high regard which is something rare for someone that's so critical of everyone else and believes most people are mediocre at what they do.
Both of them share a high level of idealization of each other. For Dirk, it's almost impossible for Roxy to do anything wrong. Even if she does, it has its logical explanations and finds easy leeway for her needs and wants.
He sees her as akin to how one would view a God, fallible and yet the only one able to bring comfort with the penalty of failing them, bringing a sense of shame and being undeserving. For Roxy, Dirk's idealization comes with romantic and sexual undertones. I would even say that this connection to basic instincts prevents her from elevating him to the same level as he does with her. They see Dirk as the fallible, weird and self-conscious human being he is and yet because of this, they find him interesting and precious.
I feel like fandom has this idea that Dirk, being this weird-ass 4D chess master, has had and would have the upper hand in whatever form of relationship forms with Roxy. And yet, unlike other relationships, he has been unable to manipulate any conversation or expectation beyond the conscious decision of not being there. This is either by never going to see her across the sea or deflecting and changing conversation whenever Roxy hints at the idea of them being a couple. The affection Dirk has for Roxy and her willingness to wear her heart on her sleeve makes it easy for her to get what she wants from him. It's a toxic situation where neither wants to hurt the other, but their immaturity and their ability to be evasive make it difficult for them to have a relationship with strong boundaries, harming Dirk the most.
While I believe idealization is a strong shared point with them with one side idealizing someone on a personal level and the other idealizing the mere idea and concept of being in a relationship, I wouldn't put comphet as the sole offender or even a major one. On a meta-level, we are told most of the culture accessible to both Dirk and Roxy comes from what is left of the mid-‘00s cultural space, with the textual implication that heterosexual cisgender relationships are expected to happen and to be desired, but as with any sociological phenomena, there needs to be a paradigm that is upheld by outside relations, either by what society in large enforces as normal or what in their everyday relations is expected. I'm not saying they are free of it. I'm just saying its presence isn't as strong. It's like an ad that goes every so often on tv, background noise that you recognize but don't think much of..
Roxy's relationship idealization is more of a lonely teen that feels the pull to connect with someone else. She needs external reassurance that she's not alone. In fact, it would have happened with or without Dirk. Dirk's guilt and feeling like he owes him a relationship comes more from seeing her as deserving of everything that she desires and being unable to fulfil that. He already has to process feelings of self-worth so adding in the mix the fact that he can't give her that makes it worse.
The thing with Roxy is that they COULD distance themself from the idea of a romantic and sexual relationship with Dirk and accept it as it is, and YET, Roxy is eager, she is an idealist and have a little of a head-in-the-clouds syndrome so yeah she could and can perceive dirk could never give her enough of what she wants, that even he suffers in doing so and yet she could still lie to herself.
I don't think she's self-sacrificing enough to be the first one to step away unless Dirk tells her to stop and even then he would not be able to uphold his boundaries strong enough, like the sea that erodes the rocks time and insistence would make enough cracks for her to sweep inside, oblivious for both of them until Roxy is in a shitty mood/situation, and gaslights and trips dirk into accepting a relationship with no strings attached "lets just vibe dirkk like nothing will change of how it is rn less just u know be" and willfully take Dirks silence and tense aura as him just thinking about it until he gives in half-heartedly, telling himself he cant possibly be this shitty to deny something that sounds good in theory, to try with no actual reproach, obviously they are both lying to themselves masterfully.
But while a toxic ship is always fun what makes me go all gogo gaga is the platonic and sensual space of their weird friendship. They are above everything the only ones that truly understand how it is to live so outside of any social framework at all. They live absolutely alone with only the idealised and distilled views of their guardians as company. In the end it's love that transcends filial, faithful and doomed to never be enough, a dance that never reaches its climax and keeps them both blundering, it's the suffering of two very different archetypes, ego-filled, anxious ridden Master Planner succumbing to a quirky, optimistic and very self-doubting person that, anywhere, could be the easy prey, it's the complete loss of power by your own choice, submitting yourself because you care.