The whole reason of using NodeMCU is the WiFi connectivity and web server capabilities. That's what makes the processor so great.
The processor as such is indeed very capable (80 MHz, 32-bit, 4 MB flash, 56 kB or so RAM) but it has limited pins (only one analog in), PWM and I2C are bit banged (so prone to glitches - rather than AVR which does all that in hardware), and it has some other limitations compared to the AVR microcontrollers.
Do read this guide on the ESP8266 to learn more about its capabilities (and limitations compared to the AVR chips). You may also be interested in the ESP32, a major upgrade of the ESP8266 (faster, more memory, more pins, more peripherals built in, etc).