I have two main points of frustration in Sims 4 with regards to how locking doors work.
First, bathrooms...in real life, before I enter the bathroom, I knock if I'm unsure whether or not it's in use and then make a decision on if I should open the door based on the response (or lack of) that I get. I would love for Sims to be able to work out if someone is in the bathroom without just barging in.
Second, NCPs coming over...again, thinking about how having guests round works in real life. They knock on the door, I invite them in. If we're doing some outdoor activity, like a barbecue, and they need to pop in the house for whatever reason, we don't need to repeat that procedure, they just let themselves in. Once they leave for the day, if they come back again, they knock again. They don't just show up while I'm asleep and start making cake (Flower Bunny, I'm looking at you).
Are there any mods out there that would allow Sims to approach doors in the game the same way humans approach doors in real life? Bonus cool points if this would also work with refrigerators. Who goes to their friend's house and thinks, I should make a full meal without anyone prompting it?!