I need to see more Japanese players because putting Greninja in top tier seems like a big think emoji
They have Lea there, the best Greninja in the world who has been winning quite a few tournaments with him. He even 3-0ed Shuton, the winner of the first Japanese major.
This just goes to show you how influential results are on people's tier list perceptions.
I do think they are overrating Greninja in Japan though. But then again they were underrating him in the west until recently when people started to realize that he is actually really good. Just not top 3 in the game good.
But from Smash 4 he got pretty much just buffs and most of them were quite significant:
- raw kill power got significantly buffed, especially on Fair (stronger than pre-patch 3DS Greninja's now), Fsmash, Shadow Sneak and Bair
- more consistent combos and kill confirms (can now kill confirm from 6 different moves, all of which are good in neutral)
- Substitute going from worst counter in the game to one of the absolute best
- his great mobility, low profile and forced low reliance on shield ever since Smash 4 (due to terrible OoS options) synergizes perfectly with the new engine
- using tilts out of a dash is Greninja's dream come true with Dtilt being his best kill confirm and Utilt following closely after
- strong recovery, which he can mix up with different angles, water push back, Shadow Sneak and Substitute
Also the removal of footstool combos was a blessing in disguise since they were never consistent vs good opponents and often got them punished for it. The best Greninjas almost never used them in practice. Now he got much better Jab lock setups which even if teched do not get you punished.
Still, being such a mobility based character with slow and very precise aerials who cannot punish well out of shield makes him very hard to pick up. Which is why you pretty much either see him solo mained or not used at all. And these key weaknesses are what's keeping him from being top tier himself in my opinion.