I think that they don't need to change the rating to M, BUT, I agree about the current game being a little immature because the emotional stakes are pretty low.
I'd like the emotional stakes of certain interactions to be greater. They sort of incorporated this into Get Famous with the Celebrity Quirks. So if a sim uses her phone all the time, she develops a phone obsession quirk or if a sim is constantly primping in the mirror, she develops a vain quirk.
What if, when a sim loses a loved one, they develop a quirk where it's harder for them to love again? Or if they experience a lot of mean interactions or bad luck they develop a quirk where they feel rejected (sort of like the Loser trait in the Sims 3). It doesn't have to be too dark or even veer off into depression, and can still keep its quintessential absurdist Sims vibe.
