There has never been one, since CS mod was created back in the days of Half Life, the reasons.. I have no idea, as it has a big fanbase the 5v5 competitive mode games. But I dont think it's gonna change now either, doesnt look like at least by how all the game devs just jump on the bandwagon unfortunately called Battle royales.
.. There is CoD and Battlefield.. but these 2 have a completly different playerbase.
I agree tho with what u meant by a competitor.. it would make Valve wake up, and update CS:GO a lot more frequently, and give fresh new ideas to the scene.. As CS:GO needs honestly, it needs like a "facewash" *source 2* would do it, but yeah.. that's not happening probably anytime soon.