The reason to stop gendering people is that when you habitually gender everyone, you will eventually misgender someone. Misgendering hurts, largely because it is so unnecessary and could be avoided with a little more education. Not everyone fits into the binary words people are accustomed to communicating within, and not everyone who does fit into the binary might look like people expect.
The solution is that instead of trying to guess everyone’s gender and sometimes getting it wrong, we can replace gendered language with gender-neutral language. That way, with a little work, everyone wins.