News Raspberry Pi Pico Converts Retro Controllers For Classic Gaming Experience

The price might seem high, but I think it is justified for a board with such an impressive list of supported controllers.

First it would need to have level-converters between 5V of the old systems and 3.3V that the Pico uses. Then a bunch of logic to be able to switch between different types of controllers.
Even if most modes are compatible with Atari joysticks, anything more complex (such as a joystick with Autofire or gamepad with two buttons) could use different pins for a different system.