Yet Pokemon Showdown and Advance Wars By Web have been running for over a decade.

I am p sure Showdown only still exists because it would crater their official VGC league if they'd shut it down. And with Champions out now it is slightly more likely they would go after it, but they know that it isn't possible to iterate and test teams as fast in it as it is in Showdown (and I doubt they plan on changing that considering the limitations seem very intentional).