I don't want to waste my time on someone who can leave me whenever. Romantic relationships take a lot of time.

You do realise that this applies to basically everything? Take education these days. Just because you invest time and money into a BA degree doesn't mean you'll end up with a good job. Or what about your own body/health? Just because you take care of it doesn't mean you'll live a long and happy life.

And it feels pointless to do when most People have a divorce and the dude is then fucked.

First, you don't need to get married these days if you don't want to. However, it still has many benefits, especially if you intend to have children. The longer you wait to get married, the more likely you'll stay together (see statistics that show that once you're 25, your marriage last a lot longer).

Why's the dude fucked? These days, a couple can decide how they want to work out as a couple. Both can work, one can stay at home, both can work part-time.... whatever works for the couple. If you expect your future partner to be home, it's natural that you'll have to pay her alimony once you get a divorce. She sacrificed her career for you and your kids and will need some time to get back into the work force (usually in a very low-paying position).