If you don't recognize differences in the female, then what you are saying is that sex is a social construct and that sex reassignment surgery is a make believe product. In such a case, feminism is a fraud product for a fake difference that doesn't exist.
Even if you can have a man and female that look physically identical in every way, and that might be possible, you still have to deal with the average distance between physical traits, which is quite real and measurable. And also the hormonal differences, and the differences caused by internal structures based upon this signaling which is often different even from an early age.
Feminism, as I have seen it, has its basis in recognizing that differences in sex can sometimes lead to only small gaps in task performance, and thus the sexes in many ways are like for like. Generally true.
Good luck being saved by an all female group of firefighters, however. I wish you all the best in that. But maybe that is the cost of "equality". More people die, and quality sometimes diminishes.
I'll believe your rejection of gender essentialism when men are delivering babies. They can obviously produce milk, and that's already well documented.
Edit: To be fair, you can absolutely have firefighters that are female and even more prepared to save lives than males. The problem is that a quota system encourages physical features rather than merit to be key indicators in hiring, which is absolutely the wrong thing. A serious weightlifter that was female could easily be an amazing fire fighter.