This kind of simpler design is available in modern SOCs. The thing is that most of the hobbyist boards are built with cell phone application processors because those devices support a wide variety of hobbyist use cases.

If you look at evaluation kits for TI's Cortex R4 SOCs, for instance, those kits don't support USB because that's not the typical use case for an R4.

It sounds like you're really looking for something with basic I2C and SPI support, which are fairly modern interfaces with simple state machines.