The title says all. The Total Drama series is the series in which there is one the most effective deconstruction of 'teenage love'. One interesting thing is that most couples were kind of established in the first episode.
First, let's take the example of Duncan and Courtney, the most popular pairing, to the point that in FanFiction.Net section of Total Drama Island there was literally half of fics there as Duncan/Courtney at one point. I don't know how it is today, but back when the hype was that big, to pair Courtney or Duncan with someone else was very rare. But it's really fascinating to see how such a pairing reached such popularity, continuation, High School A.U., crossover, name the type of fic and there would invariably be a Duncan/Courtney moment. The cries of joy of thousands of fangirls (and fanboys, to be fair) were heard all over the globe when they kissed and assumed their romance.
What attracted popularity to their pairing was the application of the "good girl, bad boy" type, there was chemistry between them. But, the problem is that not all chemical reaction has good results. The problem is that their relationship is actually a deconstruction of those kinds of relationships. The good girl is not that good, Courtney shows jerkass behavior throughout the series and ends up being a manipulative control-freak, as "Total Drama Drama Drama Island" shows and later seasons, things that were hinted in the intro video (people who portray her as an angel in fanart are completely missing the point of her character). Due to the fact she needs to control every aspect of his life, she ends bringing this to Duncan and that's where things get worse.
The second season shows how dysfunctional their relationship would be, because both refuse to change and try to listen carefully each other. In the mid-season episode between TDA and TDWT, they're fighting for the custody of a pet raccoon, doesn't it reminds you of something? And, finally, after all of this, Duncan cheats on her. Hearing Courtney saying "I want a divorce!" is a sad thing even for people who don't like her. And then, as a nervous trainwreck, she is manipulated by Alejandro until the end, she's so emotionally disturbed that she still believes in Alejandro even after it's established he likes Heather and is evil. Even in the shorts after TDWT, she is nothing but a joke.
It shows that relationships are not easy, they are not things to toy around. Neither Duncan nor Courtney had maturity to learn that people have to understand that sometimes they aren't in control and have to stop to understand each other. Neither of this happened, it was just Belligerent Sexual Tension, no development. It was expected that it would end bad if you stopped to think.
Now, moving away from them, we have Gwen/Trent. It started innocently, a Nice Guy who likes to play the guitar trying to warm up the distant, introverted goth (at first), even capable of the biggest mad maneuvers to show that he loves her and they turn into a couple, even surviving Heather's manipulations. And yet, even Duncan/Courtney lasted longer. The reason for it, it was mainly seemingly out-of-nowhere OCD, which turned him into a crazy kook. But the truth is that his bio mentions he had a lot of girlfriends before TDI. Gwen wasn't special. Perhaps he never had dated a goth, but Gwen is just another of his list, a person whom he couldn't create permanent bonds due to his psychological problems.
As someone in the Fridge page said, "So his craziness is him not obsessing over Gwen so much, but desperation over not wanting to endure breakup again, and doing everything he could to prevent that. Without a successful wingman to let him know what he was doing wrong, all he could do was rely on luck." It was a self-fulfilling prophecy.
Now, going to Duncan and Gwen, they show more compatibility than Duncan and Courtney, but it must be remembered that the first relationship ended bad. It wouldn't be a surprise if this one ended bad as well.
With Izzy and Owen, while some people consider Owen to be the Creator's Pet, his relationship with Izzy came of nowhere. There is a problem with dating the Manic Pixie Dream Girl, because she may not be fully aware of when reality starts and ends. Their breakup in TDWT followed this logic, while it's fun to have Izzy around for a short time, the consequences of having her around in the long run aren't as pleasant as it seems, like randomly break up due to her Blue-and-Orange Morality.
With Harold and Leshawna this is even more evidente. See, Harold declared his love in a very emotional context, during his elimination and regretting nothing and under the light of a full moon. It was like something straight out of a fairytale, Leshawna had to accept it. But then in "Total Drama Drama Drama Island", she admits that it was in the heat of the moment and that she let her feelings control her judgment, thus she had to break up with him, it was the right thing to do, even assuring him that maybe things can work out in the future.
And one of the biggest offenders is Geoff and Bridgette, after they started dating, their combined personalities are less than before. They were flanderized to being kissing machines. They did tone down in TDWT, but it's obvious that their relationship is another example of an unhealthy one.
Lindsay even forgot who Tyler is until later. Since it was Played for Laughs, I guess there is no point in commenting it.
When fame and money is on the line, Heather and Alejandro can't decide whether they kiss or backstab each other.
As for the other couples, they formed in TDROTI, Sam and Dakota are actually stable (and Give Geeks a Chance), and Mike and Zoey might have problems as it was foreshadowed.
Ironically, while not in a relationship, Sierra was one of the few ones that actually showed Character Development concerning romance. While in the beginning she was pretty much an unpleasant character, though not reaching Yuno Gasai levels of yandereness, she does turn less of a stalker in the end of TDWT.
In conclusion, it should be noted that the Total Drama deals with teenager and drama, the teenager years are years in which the person is still developing. And the 'teenage love' is spread in TD to remind the viewers that it's a love like in Romeo and Juliet, it starts with people not minding the consequences, but then consequences start to appear and deconstruction ensues, sometimes it fails, sometimes it fails horribly, but also it can suceed as well and then when the real conflict start, it's part of growing up and that Growing Up Sucks, right? But there is still hope, to quote Junko Kaname, "You need to learn how to make mistakes before you grow up. When you are young, you can recover quickly when hurt." And, from a global view, the characters of Total Drama can learn that.
Of course, it would be easier if they had therapists, but I guess if the viewer can understand this, it's okay.