People criticize the ML's behavior because they only see things from the MC's perspective.
The ML offered Yeonu a place to stay, while Yeonu pretended not to want to, cooked for him every day, dropped him off and picked him up after work, and treated him like a lover.
The MC never showed his true feelings, always acting as if he wasn't interested, yet he gets angry when the ML doesn't do anything, behaving like a spoiled child.
So, in my opinion, the ML did the right thing by acting that way, because the MC shouldn't get swept up in the relationship; he needs to show his feelings too. It's not up to the other person to do everything.