Trek has never done romance well.
I wouldn't say they always did it "horribly" but I can think of one instance where it was amazing. Lessons, I thought the romance angle in that was so good, I mean to this day my heart gets heavy still when I see it.
I think they do complicated "relationships" well a couple times.
Picard and Crusher, though I wouldn't count it as a romance I think the interplay in a few episodes was deep, and good.
I think O'Brien and Keiko's marriage was well portrayed.
But for the most part you're right.