You can be upset about it, but humans are dumb. Language is dumb. Terms that people have came up with, the definition that has changed over time, and how it does not relate to things in the present is dumb. Nothing will ever be exactly how you or anybody else wants it to be. It's a collective that you just have to accept as it is.

That being said, feminism has old roots when we used to pump our wives full of lithium and give them lobotomies. Treating them as equals was not something that was even discussed. You could say you were an egalitarian, but then you would have to also admit you liked people of color, or LGBTQ people. And that was a step too far for some.

Also its not excluding half the population. It's INCLUDING them. Men are included by default. It's a term that allows the conversation for how shitty women are typically treated to exist.