I don't think you're in the minority here. I think even outside Mangago most het shippers want Desir to end up with Romantica.
I do agree that she can be sweet but that's overshadowed by her tendency to nag and hit Desir, which is played for laughs (why) and she's so pressed and petty when other people show affection/interest in Desir *eyeroll* she's the typical tsundere and that's actually a pretty popular love interest trope.
I think a lot of readers would agree with you. The webtoon does amp up Romantica's scenes with Desir a lot, and the only reason I'm shipping Desir/Adjest in the webtoon was because I'm seeing them through novel goggles. There's a lot more of Desir/Romantica, which I never understood until I read the note about some stuff deviating from novel.
Basically, if you're shipping Romantica in webtoon, it makes sense. Whereas in novel, Adjest is portrayed much better.
to be fair, I would, personally, prefer no romance with desir to begin with-not with the other teens at least. Not now that he has so much more emotional development than them, and already lived as an adult man.
I like Romantica more than Adjest!(As a love interest.) There! I said it!
Adjest would just be so typical. I like the idea of romantica, whos sweet and cutesy, and very much like a secondary love interest, to win over adjest who-if they end up together-would have been so predictable and cliche. Idk, I also think that in the webtoon, romantica and desir have a lot more chemistry, while adjest is more of a companion.