I definitely think that there should be more YA books that don’t include romance, because good friendships and relationships are just as important (if not more important) than romantic ones and have just as much right to be depicted. I think if the plot is engaging, and your lead characters have great platonic chemistry (good or bad), people will be hooked. In fact, in my favorite series, there really aren’t any romantic subplots (Well, there is one -kinda- but also not really? In the end everyone just winds up being friends and the ‘romance’ part isn’t really important and pretty much used for comedy, so… ).
That being said, though, I do enjoy a good romantic subplot if it’s developed enough and seems to make sense. And I am all for portraying a good, healthy teen romance that stays consistently clean (seriously, this shouldn’t be so hard to find), or showing an abusive relationship for what it is (not romanticizing it). If the relationship becomes more important than the plot, then I tend to get bored (unless the plot was also mind-numbingly boring), but sometimes it’s nice to take a small break from the actual plot with a cute romantic subplot.
Personally, I don’t really like flirting that doesn’t lead to some kind of romantic subplot, because I feel like it’s kind of ‘building up’ to nothing, which yeah, can disappoint readers because there’s no payoff (the only exception I can think of is where a character has been clearly characterized as flirtatious).
I think the best advice I could give you as a writer is to let it develop naturally. I had a project where I didn’t include romance initially, but then I realized that the way I had written one of my characters would make a lot more scenes if he had a crush on my protagonist. And so their romantic subplot was inadvertently formed. On the flip side, I had a fantasy project that was supposed to have a pretty significant romantic subplot, but it just took away from the story I wanted to tell that I scrapped it, and now every main relationship is strictly platonic.
So if it makes sense with your characters and fits naturally into your story, then I think you can totally go for it. If you find that writing romance makes you want to pull your teeth out, then there’s no reason you should continue writing it.