The fact that it is M doesn't mean you must have sex scenes. If you just put sex scenes to shout "Look at me! I'm an adult game!" it is not very adult. it's quite childish in fact.

Larian's Biggest Oversight, what to do about it, and My personal review of BG3 EA
"74.85% of you stood with the Tieflings, and 25.15% of you sided with Minthara. Good outweighs evil, it seems."