Why is there always this whole discussion about FF? This is also being discussed in Era and it leads to the same false assumptions that a day 1 PC release would lead to significantly better numbers. That was not true for Persona, Forspoken, Like a Dragon or Dragon Quest 11. It doesn't make sense either, since FF7 Remake sold significantly better than Rebirth despite being PS4 exclusive, and the PC port afaik didn't lead to massively more sales. On the contrary, PC gamers were crying again because SE wanted full price.
It also makes little sense to compare Rebirth's numbers with Remake. Remake was released in April 2020, right in the middle of the Corona lockdown and in the last year of the PS4. At the time, the PS4 had sold over 100 million units and was cheaper than the PS5, which is around 60 million. Since Spider-Man 2, also a PS5 exclusive, is selling significantly better, the reasons are obviously somewhere other than PS5 exclusivity.
This is my subjective opinion, but Final Fantasy as a brand is no longer particularly interesting thanks to FF13 and at least since FF15. This constant reinvention of the brand has ultimately not led to more success. While I still thought FF16 was pretty good and had a lot of fun playing through it, I'm wondering what I'm doing wrong with FF7 Rebirth. At the moment I'm just struggling through the game. This is due to the rather exhausting "open world" maps, the non-existent story and the chaotic combat system. I won't even start on all the technical deficits like LoD or muddy image in performance mode. In short, I really hope the rumors are true and FF9 will be more of a conservative remake including turn-based battles and brilliantly staged summons. When I look at what F2P titles like Genshin Impact or Honkai Star Rail are delivering, SE will have to think about where they want to go with FF at some point.
In my opinion, the series would probably have disappeared into the abyss long ago without Sony. Nothing new about Nier for 7 years, even though it was a surprise hit, and DQ11 is almost 6 years old. A DQ8 remaster on all systems would have been useful as a bridge until DQ12 (if it ever comes out). But SE doesn't seem to be making particularly smart decisions. Perhaps Sony will lose interest even with the moderate success of FF and SE will bring FF17 back to being multiplatform. I wouldn't be surprised if there is another chaotic development like with FF15 and currently DQ12.