I'm browsing the Game Dev stack exchange in Safari on macOS. All the buttons for posting questions and answers are light gray with white text. This is both difficult to read and makes them appear disabled. Here's what I see:
It may just be my aging eyes, but I can barely read that. If the text were black, that would solve the problem, I think.
Furthermore, on macOS, here's what a disabled button from the OS looks like:
The text in that disabled button is more readable than in the enabled "Post Your Question" button. Regardless, the white text on light gray background resembles the disabled button enough that I think many users will assume it's not working.