>>48897756>>48897778>>48897774I don't think anyone's denying that Gen 6 was definitely the start of the downfall considering that it signified the identity crisis that it was going through and exemplified many of the symptoms that evolved into the current state of the series-- but at the same time, Gen 7 was really what ended up solidifying the new direction with practices like removing the core gameplay elements that were present in Gens 1-6 along with the National Dex-- and one could argue the reason for that may have been partly due to Pokemon GO, but it's also important to consider that shifts in the franchise were happening as far back as 2015 when Iwata died as he would no longer have his nose in TPCI's affairs.
It's more appropriate to say that Iwata's death is what caused irreparable damage to the series since that is the most likely time where they would have shifted development of Sun and Moon from a successor to Gen 6 into its own Yokai Watch spinoff-tier thing.