I can't build pycryptodome just with pip, i need to install python-dev and gcc and all dependencies from those just for this, can you make it recommended like rtmpdump? Only a few plugins need this.
See the install documentation:
https://streamlink.github.io/install.html#using-pycrypto-and-pycountry
Or setup.py:
https://github.com/streamlink/streamlink/blob/0.7.0/setup.py#L28-L33
It's for the greater good, it's easier (for us) to include it than to exclude it. The easier it is for us to maintain the better it is for everyone, in general. You can use pycrypto as @bastimeyer pointed out, which is probably available in your distro's package manager.
I'm going to close this out, we've had this discussion previously and the workaround is pretty easy.