I also agree that games should always be multiplatform and also please understand that I have no stake in this if it is exclusive because I am getting this on Switch either way. I say this as someone who beat P5 twice on my PS4. That being said, I strongly disagree with your point on the Vita because the writing was not on the wall. 6 months (the time between the vita releasing and P4 Golden coming out) was far too early for the writing being on the wall. The situation is just not comparable.Vita sold less in its life than Switch did its first year, the writing was on the wall when Sony basically abandoned it after launch. Hell the Vita was the first system I ever sold as an adult (and later re bought when I became a heavier collector). Nintendo fought back early with 3DS and it was the sequel to the DS, it was the obvious victor to anyone with common sense.
Keep in mind, I'm of the opinion these games should always be multi platform, so I have no desire for Persona fans to be slighted, I just understand the business sense of it. It also won't surprise me if this is 'exclusive' and then a bit later gets a PS4/PC port, etc.
I'm actually curious how many people on this forum own a PS4, Persona, and don't intend to own a Switch, I actually would have assumed that was not typical.
As far as business sense goes, I can wrap my head around that. I just don't think the Vita or previous Persona's releasing only on handhelds is a good comparison for the situation we are in right now. I get why people would be upset if it is exclusive.