It's a different situation since Forza 7 was initially designed from the ground up around loot boxes and microtransactions. Eg progression, rewards and other things that were previously simply bonus linked settings or fixed in nature, were redesigned to be luck based modifiers and more grindy in nature to further promote the sale of microtransactions and loot boxes (something that fortunately never came to fruition). They were only changed or omitted because of the outcry.
GT Sport is different because the game has not been and never was designed from the ground up in this way, nor is this MTX inclusion going to change the way progression, rewards etc currently work. There have also been no MTX for a year, and there have been more content updates and tweaks than were ever promised too, so there's good and bad, but it's obviously still mostly good.
Ultimately, I don't think any other racer or GaaS game in history has had the kind of free post game support that GTS has had, which is why the majority of people who actually own the game in this thread aren't too bothered by this announcement. Continued content support is the more important consideration, and it's probable Polyphony never foresaw supporting the game in the way they have this long after release, hence the change of plan.
