You cant please NTR and romance fan at the same time.It will lead to disaster.
As an NTR fan I agree with your statement to an extent.
I believe that it is more accurate to say that trying to appeal to NTR fans and anti-NTR fans "During Development" will (probably) lead to disaster.
The argument is that it takes twice as long to develop a game with and without NTR because half of the game is unplayable for most people. From my perspective it makes the NTR routes more rewarding knowing that the other path could've led to romance. Does it have the same effect on people who choose the alternative? Maybe. Probably not.
As an aspiring developer I have a great deal of interest in this topic because I like the appeal of a NTR/Non-NTR path game. Based on the fact that most NTR fans could play a romance path without vomiting from disgust the best solution that I have been able to come with so far is to: create a game to it's completion and then add the NTR path afterward.
I feel that the community is overly harsh on developers pertaining to this topic. In the end of it all I feel that if dropping in NTR content along the way helps to inspire them to continue their work; Do It.