Hey!
I'm playing Stellaris since v1.0, and I always wanted to try playing a galaxy where only humans (or maybe only humanoids) exist. Every time I asked about such mod, there were players who would love to play it too, but the mod was never there.
There is a way to 'simulate' it by making many species by myself and forcing them to spawn, but it has many flaws.
If some modder creates such mod, I'm sure it will become a popular one.
Also if anyone knows of such mod, please let me know.