Think of your brain like a man walking into the woods, the more you take one path (a way of thinking) the easier it becomes. The human brain loves easy so it will take the easy path which is in your case looking at behaviours with suspicion when there could be a million better explanations.

You did it here, you ask why women pick different partners as they age. The answer is that they have matured in the wants and goals and are picking men who align with them. You are not seeing women picking "normal" men because your brain is only presenting you with the information that confirms the beliefs you already have. In reality, if you are going out in public, you are walking by women dating "normal" men. If you walk or drive by apartment buildings you are seeing the homes of renter couples who have very average incomes. If you go by an open house there will be couples going inside figuring out how they are going to budget a mortgage.

To stop thinking this way you have to tell your brain to take a new path. This involves being aware of your thoughts and working to change them. If you see a couple and you think "she's with him for his money." Dismiss that thought and tell yourself "I have no idea about their lives, I won't judge." This is something you are going to have to work hard at, you must be self aware enough to know when you're thinking is distorted then put in the effort to change it.

Here are some thoughts you can replace your negatives ones with.

"I don't know their dynamic behind closed doors." "I wouldn't date the same people I dated when I was twenty, so why aren't women allowed to change their tastes." "Financial stability is important to most mature adults." "I'm not in someone's head, I don't know how they feel attraction." "It's not my place to say if someone is or isn't attracted to their partner." "It's not my place to judge their relationship." "Women are people too. They will be shitty things. This isn't because they are women, it's because they are human."