@Purplelibraryguy
People are capable of some pretty amazing feats sometimes, so it's not surprising to see some people buck the curve. I wouldn't say it's impossible to make a relationship work with people who are very different, but it is playing on hard mode.
@Kekitus
Certainly you're not going to find two identical people anywhere, but it's generally only the things that are important or strongly valued that make a difference one way or another when it comes to being alike or opposite. Honestly, in my experience, introverts may have trouble getting started but can get really attached long term. Unfortunately, there's no single silver bullet to relationship success. Just a bunch of things that can make your life harder or easier.
Statistically speaking, being on the same page when it comes to important things tends (with a generally normal distribution) to produce relationships that are reportedly more satisfying and last longer. When faced with problems, it really helps to be on the same page as your teammate. Let the less important things like hobbies and favorite genres provide the spice of learning stuff you didn't know about someone.
Having a good match helps, but some people are just bad at relationships in general, are serially abusive, etc.