[tyingq]

Sure, though 240Mhz, 32bit, optional gobs of PSRAM, etc, aren't usually what comes to mind when you hear MCU.

Edit: Yes, you could even use an ESP8266, though 32x128x3 plus X bits of PWM brightness would mean being limited to drawing from storage rather than in-memory manipulation. I'd jump right to the WROOM type devices with PSRAM.

[sokoloff]

If you need a microcontroller with networking (such as the train sign would), I think the ESP32 (or older/cheaper/less capable ESP8266) is one of the first that comes to mind for most engineers, especially those who aren't full-time firmware engineers.

[anigbrowl]

You are quite right that the ESP is way over-specified for many tasks, but it's not like the uC is gonna quit and take a more fulfilling job elsewhere. You can get tiny boards for close to $5/ea, or under $5 if you don't need the USB connector. - and that's in single-digit quantities. The hardware configuration is very flexible, eg if power consumption matters you can run it a lot slower, switch off subsystems you don't need, use a watchdog timer to simplify exception handling etc.. There's a rich and constantly expanding SW ecosystem so you can get to a working prototype very fast.