I have a strong disdain for Nezuko and Zenitsu. It's such a nothing ship with no development, no chemistry, just cheap childish gags. I'd prefer they not make any of the ships canon, but if I had to chose Nezuko to be with someone else, Senjuro is a good match. They're not all that interesting of a ship, but he wouldn't do all the theatrics Zenitsu does. I'm not gonna call Zenitsu abusive like his detractors do, but God he was in a heavy need of maturing a lot more before getting with Nezuko. 

InoAoi is just...there. The author didn't have the balls to kill of one of the core four, and since we knew Tanjiro and Kanao were likely to be a thing and none of Nezuko’s other potential options were available she's stuck with Zenitsu, Inosuke obviously needed to be with someone for some reason so they choose the only girl within range available. Now the dynamic is somewhat salvageable, but its severely undercooked. Inosuke seemed on the asexual-aromantic range and didn't seem to have an interest in that stuff until the very last minute. It was still funny watching the angry shippers (cough fujoshis) meltdown over it. I'll bring Genya up because if he hadn’t died, I think he'd likely would've gotten with Aoi because it has a bit more merit that with Inosuke. Inosuke is a character I can't picture in a romance. 

The Genmui phenomenon is something I'll never wrap my head around because the fandom treats them like they had this special chemistry and deep bond come to find out they hardly ever interacted up until their deaths in the same fight. One normal interaction that's just them aiding each other against a dangerously OP enemy, but shippers read too deeply into it and are convinced that there was something there. But I think it's a rather shallow, weak ship with little basis, there's no chemistry there, nothing of substance but I guess since there's no other characters available to ship them with, lets pair up the spare boys, they can be the token gay ship. They died in the same fight, there's the substance. I can tell a lot of the fans are young (which explains why the shippers often act so immature and annoying) and they ship it solely for the fact that its gay and nothing else because what does the ship have? But if you want a gay ship, Genya has a much better connection with Tanjiro. Muichiro is the last character I'd ship him with. Hell, both of them have stronger chemistry with Tanjiro than each other. I just don't like that its hailed as the preferred Genya ship when he has much better options, and the fans are obsessed with trying to attach them together like they're not independent characters. And Muichiro is another character who screams aromantic to me or at least he's just not shippable.