Tatoruzu one of the reasons I hate that Nickelodeon bought off the TMNT. There were never any turtle-human romances before this (that I know of) but when Nickelodeon bought the TMNT that all started. Mutant Mayhem and 2012 are the worst examples of this. The only romances Rise has are the ones between Big Mama and Lou Jitsu, which was a one episode focus. The love between Hypno and Warren Stone, obvious parody of censorship and also a one episode focus. And the sub textual hints that Draxum was into Lou Jitsu. None of these involve the turtles.
Looking at the 2012 show, there was really only one romance that was good and I liked, that being the relationship between Raph and Y'Gythba (Mona). So far, Raph has been the only turtle that hasn't had any human love interests through the whole franchise (THAT I KNOW OF).
I don't really see Donatello x April as a romance, even though Donatello is crushing on April. The only reason I say this is because of the fact that April seems to like Casey Jones more than Donatello in a romantic sense. Some people say April is leading Donnie on with the cheek kisses and hugs, but I personally believe she's not. People mostly talk about the fact she just wants Donnie to think she likes him back, but I personally believe she just doesn't know how to turn him down. She's an awkward teenage girl, and as I've been in her position before, it feels terrible having someone like you and they've made it obvious to all of your friends, so it makes it harder to turn them down out of fear you'll look like the bad guy. The uncomfortable romance.
Leonardo x Karai honestly could've been a great romance if they weren't related and if Karai was mutated before they met (when she was mutated into that snake thing in season 2). The writers should've either chosen a love interest route or the family route, not both. The controversial romance.
Michelangelo has two love interests, Renet and Shinigami(I think that's how her name is spelled). None of the romances really go anywhere. Renet plays along with Mikeys flirting because she's basically his idol in the future, and Shini never really responds to Mikeys flirts, she just ignores them. The most boring romances.
Raph and Mona are ADORABLE. The only good romance in the show. Their relationship isn't turtle on human, which is an amazing save for the romance. The only thing about this is the lack of screen time, and even then this might be a good thing. Good romances with tons of screen time can easily go from fan favorite to the most annoying thing in the show. (Example; Donnie and April).
If we're wanting to include Splinter and Tang Shen, I don't really like the romance. I mean, she's basically just to help fuel splinters 'man pain' arch and to kinda fuel the incest backstory for Leo x Karai/Miwa. I personally don't like this romance, but to each their own.
What I'm trying to say is, mutant on human is basically zoophilia/beastiality, and since that's the case, people crushing on the turtles is also considered beastiality. Some people could disagree, but again, this is just MY opinion.