Tbf a streamer I follow named Korea plays Genji almost all of the time, and he's really good and carries games a lot. If it works for you, no reason to change.
That being said, he will change if it isn't working.
I have a couple of friends that are determined to keep equal time on every character, which honestly strikes me as even more strange than only ever playing one. I don't know, I don't get imposing limits on yourself. I also don't think it's bad to have a main seeing as it's perfectly possible to have one and still be well-rounded. Everyone should just play who they like.
Unless you're a Hanzo main. Jump into the well on Ilios, if so.