I agree with you for the most part, @Cinebar. Not so much mark as family member, but personally I would like to romance lock different Sims. However, we do have some tools in the mean time, including a social that wipes the romance bar ("Agree to be friends.")
So I do challenge your claim that we do not control the Sims 4, since in the scenario you mentioned I can not only use this social, cheat to add an unflirty trait, separate said Sims, and/or just disable autonomy altogether. Plus, flirty Sims do not automatically flirt with proper children, so no grooming.
