I completely understand what you're saying creating eroticism isn't easy, and I’m with you on that.
But let me be blunt: can anyone really have a wank to these sex scenes? Honestly, they’re not even long enough for me to lower my underwear.
If the developer isn’t able to build proper sexual tension or eroticism, then at the very least, they should spend more time adding visual depth more images or frames to the scenes they’re trying to portray.
Let me give you an example: the game [LISA]. In that, a sex scene is thoroughly represented. The viewer has time to warm up and, frankly, enjoy a satisfying and dignified wank experience.
I got a little bit grumpy because I like this character.. i do not expect Oscar award plot.. but at least of minimum standard in portraying sex scenes..