I certainly have some pairings I will only accept if I'm looking to read shipfic for the canon in question. But the fact that other fans ship other character combos in those fandoms has honestly never seemed that relevant to me? In fact, my OTPs for some of my longest fandom loves have even shifted over time...and even for cases when they've remained constant, someone being into a different pairing has never felt like anything that strikes at the very heart of my identity. It's just someone else being into a different thing than I am, which happens all the time in the world.