Even if you hold the position you stated and wanted that change, we can't deny someone rights in the current system for some future better situation. There is an immediate and real world problem that needs to be addressed while you strive to implement your preferred system.
Part of the reason there is a push for gay marriage is because the alternatives (civil partnerships, "DIY" marriages using contracts) and they've failed to provide the necessary protections for couples in the way marriage rights seem to.
There is a compelling societal need to be able to say "here are people who are in an intimate, long-term trusting relationship for the purposes of decision making, finance, tax and so on".
I wish you luck in your campaign to find a compelling and convincing political and intellectual argument for something that would serve the social goods that marriage does and would effectively replace marriage for gay and straight couples. Until then, I'd quite like to be able to get married to someone of the gender I'm actually attracted to. (And as of Saturday, I will be able to, thanks to the marriage laws in England changing.)
And yeah, making this argument widely compelling is going to take a lot more than luck. Immediate short-term realities tend to dominate over long-term abstract ideals.