Many many countries have payment methods that only exist in that country, but make up a large percentage of online payments within that country. I’ve personally seen Adyen chosen over Stripe at a few companies that were aggressively expanding internationally for exactly that reason.

Adyen seems to implement every payment method you can think of. And if you don’t want to implement them, their white label payment page is able to dynamically show payment methods based on user location and merchant preferences.

This is seriously lacking in terms of what's available on the market in Japan now.

No support for point payments (like RakutenEdy payment), neither Linepay, Rakupay, Merpay, Paypay and other QR payment providers, nor Suica or Pasmo pay, and this is still just the tip of the iceberg what's available in Japan and missing in Adyen (Nanaco, Waon, dPay, auPay, etc). Just saying, before you drink too much of that kool-aid.

I would assume it's lacking similarly in other markets too.

Yeah, and how many payment providers provide all that and all the rest that Adyen provides?

I'm drinking Adyen kool-aid because I worked for a company that needed payment methods in Japan, and in India, and in Korea, and in Latin America, and in Europe.

Adyen provides all that. Yes, they will not have 100% of local providers, but it's still 100% better than any competition.

GMO PG is famous option for EC but more enterprisey. https://www.gmo-pg.com/en/service/mulpay/

International is actually really important. It's not just that you are currently international, it's do you have any plans to go international ever? Because if so, you might have to rewrite your entire payment stack at that point.