Well they always had a recourse. Get married someplace else. Go to a different church, or if your sect forbids it, get to a different sect, and if your religion forbids it, make your own sect, and if that's too much work, just get a civil marriage.
I know it's not quite that simple, people get very hung up on where they spend their Fridays, Saturdays or Sundays, but people usually have options of some sort.
Sure, but one could say the same for "whites only" businesses in the American south. African Americans could just eat, fill up their gas tanks, buy clothes, etc. "someplace else." The Civil Rights Acts makes it clear that the people (or at least the government) does not endorse that form of self-determination.
Except that religious tolerance, including tolerance for religious organization's religiously grounded specific discrimination stances, is specifically enshrined in the Constitution. Businesses have no similar or even remotely analogous protection.
Drawing an analogy between an organized religious organization like a Church and a business like a restaurant is a fundamental misunderstanding of the law. This specific dividing line has been held up over and over again in cases where religious organizations incorporate a business entity, and then wish to push particular discrimination policies specific to their practices into that business.
A White Supremacist church is free to be discriminatory, but the bakery it owns and runs as a separate business entity is not for example.
However, IIR, a religiously owned organization, like a corporation, may choose to discriminate based on religion. So the White Supremacist Church's bakery, let's say it's Lutheran, may choose not to hire non-Lutherans at its bakery. This was actually held up by SCOTUS in a 1987 decision for a Mormon church owned corporation.
I know it's not quite that simple, people get very hung up on where they spend their Fridays, Saturdays or Sundays, but people usually have options of some sort.