Yes but so are NRF24s aren't they? I used, or tested, ESP-01 modules without flashing a new firmware. There are so many models of 8266 that it is difficult to say what they are not. But they use WLAN frequencies. ISM band 434MHz devices are easy because serial bus is usually easy.
What ?!!? They ARE ? I did NOT know that. I guess anything is possible with enough knowledge and experience with time. But yea, I'm looking for a straight-up wireless MEDIUM range (just my back yard for now) reliable serial port for my projects. Modifying an ESP and playing around with the code is a project for itself.