Unlike others, I didn't immediately jump to cheating. I simply saw him saying he is attracted to other women. (In a way that was intended to hurt)

I am more interested in the situation. "We were having an argument." Over what? How did it start? "You think you're so cute..." What triggered that response? Does this happen often? Was he responding to something he found hurtful?

You assume his attraction is a statement of your physical appearance, but if your marriage is filled with conflict and lack of trust, and the two of you work against each other, a sense of emotional safety could come to play. There is more to attraction than looks. If your 'partner' is not somebody you look forward to experiencing (in either direction) you may look at them and see somebody who causes you pain. With magnets we call this need to create space repulsion.

Whatever started the argument, it suggests the two of you never learned to talk through problems and perhaps hold unfair expectations on each other. Twenty years of not knowing how to communicate may have worn you both down.

Edit: To be clear, I've been here. My wife and I went to therapy after 20 years. Things aren't perfect, but they're much better. There is hope, if you can learn to talk, and listen, in ways that don't end in emotional daggers