Oooh more 'ignored content'.
People who carry grudges are losing out on life.
Rousey is a public figure, an entertainer ( as all fighters are whether they realise it or not, some do, some don't) so people either like her or don't. That's life, it's not an insult to her country to dislike her, it's not a sign of jealousy, not a sign or mental instability just as it isn't if you do like her. On the scale of one to ten of her importance in my life she's about a minus 100. As for her being a pioneer she was one of two female fighters who comprised the first female fight on the UFC, who can name the other fighter?
The UFC saw money in putting on female fights, she and the other fighter were chosen as the first, that's not pioneering. She wasn't in there in the early nineties fighting to get an MMA fights put on, let alone female fights, she didn't have to find somewhere that would train MMA again let alone female fighters, she didn't have to persuade promoters to give her fights. she's had 13 opponents in 6 promotions, that happened because of the female fighters who went before, fighting not just in the ring/cage but to get promoters to take female fights, to match them and actually find opponents. it was incredibly difficult in the 90s to do any of this. Female fighters often had to travel to Japan to find suitable opponents, and all over Europe. There was no money available either, we had to club together to get a female fighter from here to the US to fight, she only got expenses paid if she fought, her opponent came in well over weight ( as usual) but to get the money to pay for the hotel and living expenses in the US our girl had to fight, lost of course with her opponent being that much heavier ( this sort of thing doesn't help female MMA either when it's tolerated) The upshot of this is today people only see the tail end of many fighter's careers and because they didn't have many fights assume they weren't good. You could also ask yourselves with these odds against them why female fighters carried on trying to break through the barriers. That they did in the end and didn't benefit so much from it is what makes them pioneers so that those who followed, like Rousey, didn't have to have all that before embarking on what is now a career in MMA rather than it being an odd and disapproved of activity for women.
So, no, Rousey isn't a 'pioneer' she's one of two female fighters who were first in the UFC. Notable certainly, and her career has been meteoric leading, I expect, to more opportunities but pioneering, no, not in any sense.