The addressable LEDs aren't typically just bit banging GPIOs. There's no clock line with common protocols in the space like the WS2812, and they're very susceptible to jitter. Twiddling GPIOs from user space is basically a non starter.

I've had success though with using the MOSI line from a SPI master and carefully crafting the bit pattern and timing to get the waveform I want. It takes some manual work though, more than what you get from user space.