I worked on developer experience at Stripe for a few years.
What really happened is that Stripe's products used to be simple. If you're only accepting credit cards and only serving the US market, the API surface is extremely simple. Once you start going multinational and accepting different types of payments it gets much more complex.
For example, OXXO gives users a barcode and lets them take it to a physical location and complete the purchase, so instead of a system like Visa which can confirm a transaction in a maximum of O(seconds), you also have to support methods where confirmations take O(days). Building custom API endpoints for each payment method isn't realistic, since there are hundreds worldwide, and merchants want a single integration point that can support anything from credit cards to coupon-based systems like OXXO.
TL;DR -- Stripe's APIs are definitely more complex now, but it's not because of poor design, it's because they simply have to be in order to serve the customers and markets the company is now reaching.
What really happened is that Stripe's products used to be simple. If you're only accepting credit cards and only serving the US market, the API surface is extremely simple. Once you start going multinational and accepting different types of payments it gets much more complex.
For example, OXXO gives users a barcode and lets them take it to a physical location and complete the purchase, so instead of a system like Visa which can confirm a transaction in a maximum of O(seconds), you also have to support methods where confirmations take O(days). Building custom API endpoints for each payment method isn't realistic, since there are hundreds worldwide, and merchants want a single integration point that can support anything from credit cards to coupon-based systems like OXXO.
TL;DR -- Stripe's APIs are definitely more complex now, but it's not because of poor design, it's because they simply have to be in order to serve the customers and markets the company is now reaching.