Common complications and imperfections in relationships often have to do with incompatibility of some kind. That could be that two people's personalities just don't click, that what people want from the relationship, long term or short term, isn't compatible, that there are important values to one that the other doesn't share, and so on. Those are the kinds of complications that could lead to a relationship ending.
In terms of the the smaller, common complications Mo is referring to, those can take on all sorts of shapes as well. People can have quirks or habits that annoy you (and you can have those same things), and there can be hiccups around everything from communication to how you put the dishes away. Part of navigating romantic relationships is figuring out when those little problems are things you can deal with or talk about and when they're actual deal-breakers.
Rather than thinking that the fact there isn't a perfect partner out means you shouldn't bother dating, what if you thought of that fact as opening up more potential, awesome relationships for you? Yes, there's not a perfect partner out there waiting for you, but that means there are lots of people who are almost-perfect. People who you'll think are awesome and you'll love being around, even if their are conflicts or incompatibilities that cause the romantic relationship to end.