Honestly, it was important for me to get married for pretty much the inverse of the reasons its important for you not to.
Society used to be patriarchal. Marriage is a legal contract for how families are formed that is of a patriarchal time, but so are millions of other things - women used to not be able to own property, or vote, we changed things that were unequal and remade them rather than getting rid of them or doing without their protection.
I view my marriage as a feminist act, though I'm sure people will disagree. Neither of us changed our names, we did have a wedding and were both walked down the aisle by both parents as we liked the family symbolism, we made sure there were equal numbers of male and female voices speaking at both our wedding and the speeches, because we got married in Ireland both our mothers info was on the wedding certs as well as our fathers. We both kept our names and agreed to double-barrel children, we continue to have an equal relationship regarding housework, earning, etc. I was very clear I would not buy a house or have a child unless we were married because I've seen women, in particular, live to regret that decision and I think its important all women get as much protection as possible, though I appreciate there are some financial situations where it doesn't apply.
Importantly: if either of us bugger off on the other, a court will give us a certain degree of protection, esp re: pensions, etc. If either of us dies, the other is entitled to the state pension, the house, a million and one things automatically. For me its a way we demonstrate love for each other - not the fancy dress or party, but the legal protection part.
I totally get you might not see it this way, but to me the patriarchal trappings we attach to marriage reflect our fucked up society, and would attach to civil partnership if that because the de facto alternative. The way to fight back is by having marriages that are true partnerships, and chipping away at all the expectations and tradition that are outdated while keeping the bits that make sense. But if I can't convince you of that, I'd at least slope away and do it in a registry office without telling anyone, because a couple of hundred grand to the tory government in inheritance tax you don't need to pay is unlikely to be spent in ways that line up with your principles either!