i don't think they are any good. If its a no, then listen and go spend your energy somewhere more worthwhile.
While it is intended to allow for more in-depth interaction, relationships, and weight in a character's actions, it almost always is instead used to make someone look better.
I always feel so bad for the second lead… they deserve so much better. Imagine trying to woo the person of your interest for YEARS only to learn they used you for character development.
They are the kind supportive safety net that is needed to create jealousy, conflict, heart-wrenching angst, and support.
In a lot of these books the male love interest isn't allowed to have a personality so it has to go somewhere. In Romance novels, I've found that it's pretty rare for this secondary love interest to be less interesting than the primary one.
There are only so many sources of conflict that make a romance novel longer without changing the genre or repeating.. Family, Society, some kind of major disaster or other event to separate them, rival love interests on either side... If a romance novel is long enough it'll have each source of conflict show up and probably repeat a few along the way.
I don't know how true this is. A Romance novel can have the same kind of conflicts that you'd see in just about any other kind of book. If a particular book has trouble generating interesting conflict that's going to be the writer's fault; it's not a limitation of the genre.
The more focus you add to other types of conflict (Like say, some big war that the lead characters have to fight on), the less focus you put on the romance, which kinda leads to what Fluffums said about changing the genre. Sure, you can add different sources of conflict and give them a minor focus to still get the main focus on the romance aspect of the novel, but... Almost anything that you try giving a minor focus to will probably just have a consequence that is related to one of the things Fluffums listed in his post. It's not about having trouble generating interesting conflict, it's just being aware of what are the limitations of one genre and what kinds of conflicts work best with it without taking away too much of the focus on the main point of the genre... Romance. Even if the conflicts are interesting and well-made in their own right, there is a pretty decent chance you'll start tiring/boring your reader if they start taking too much time away from the romance that your novel should be focusing on... Because that's just not what the readers signed up for, and it's not what they wanted to see in the novel.
I think the foundation of the romance genre is severely messed up. Like toxic stuff. Generate drama, do not write anything about boring healthy fun relationships.
But there are tons of Romance novels that do just this, and nobody mistakes them for something else. In fact, some of the most famous Romance novels out there are very good for things other than just the romance part. I think this is all wrong. Romance isn't a limiting genre at all. and it can be paired with just about anything. Using pure romance for conflict is not infeasible, but it's a really bad idea for most writers because they're not going to have the ability nor the inclination to do it properly. Taking advantage of the kinds of conflicts in other genres fits perfectly because it lets the writer create conflict and build an interesting story without having to take any real risks. In fact I don't think that I've ever seen a Romance novel be even halfway decent that doesn't do this.
You could flip things around though and argue that avoiding other types of conflicts can limit what you can do with the romance itself. For example going to war could be the very thing that makes the characters bond in the first place and fall in love. I guess it depends on how good the author is at interweaving the romance with other things, and not just putting both things in the same story.
... You should try reading more shoujo before saying this. It's not that hard to make a good romance story revolving entirely on the romance. You're really underestimating the average writer. Romance is not a particularly hard genre to write about... It's probably one of the easiest ones in actually. Oh, that's a good point~ I was thinking of a story that had an established romance as the status quo, and then having their daily lives broken by an external conflict, but... If the whole story already had this different conflict from the getgo, you can definitely intertwine both things well~
Second leads exist to comfort the female lead, give warmth to them and let the male lead be jealous. their existence are basically useless sometimes though they are much love by other people. For me they just want to give us second lead syndrome HAHAHHAH
This is my point as well. These stories are as much about these other elements as they are about Romance to begin with, and much of a story's tension will come from these other elements. Old school shoujo understood this very well so the standouts of the genre use this other subject matter to generate much of the drama. And you can see this quite clearly in all sorts of works like Glass Mask, Aim for the Ace, Hana Yori Dango, and Sailor Moon.
What about romance that focuses on how the leads learn about accepting each other's flaws or building a healthy relationship together? The focus can be on each side of the leads without involving a third wheel?
Oh yeah, the conflict itself can be the very personal flaws that the characters have and that the other can struggle accepting~ Somehow I forgot about that one. That's a pretty common one even~