I thought Congress could overturn a SCOTUS decision by legislation and a vote? Am I wrong?
No.you are not wrong.
But since this ruling is that there is a constitutional right to homosexual marriage , it would tskens constitutional amendment to override this. That won’t happen.
It has to be a constitutional amendment.
Yes you are wrong. Congress cannot overturn a decision. But court decisions are based on laws, and laws can be changed. This particular decision was based on the Constitution though and would require a constitutional amendment.