I’ve got a question... how can y’all see him with the redhead??? Mr photographer is cl...

Everything is more complicated than that.
The photographer started to act rather jealous and pushy because he is insecure which isn't the positive sign in their relationship.

Tru but the readhead is the reason he became so jealous and insecure, he intimidated him several time and don’t even get me started on the anger issues. It’s his fault for not sharing his feelings earlier, let em be happy, isn’t that what you should want for the person you love?

But like he hasn't been contacting Haesoo for a long time now...? He gave him the space Haesoo wanted.

Also Haesoo could have also confessed?

Tbh if you'd read carefully Taku was the one before photo session that firstly started smirking at Joowon (who was taken aback by that) because he knew that's the infamous step bro who had relationship with Haesoo and Joowon didn't know that Taku and Haesoo were involved. And then he started getting personal. To most likely riled Joowon up.
Of course no one is going to make excuses for Joowon showing at Taku's apartment and making a scene.

But he is growing, he is reflecting on his actions. There is character development.

Taku knew that it's too soon for Haesoo still he begged him for relationship. It's not a sin, he is only human but now he has to face with consequences, with option that there is a possibility that Haesoo won't fall for him.