My current understanding is that toxic masculinity is about an attack on and suppression of femininity. It's a key foundational part of the war on women. It's about emphasizing the strength of "masculine" traits while at the same time putting down those assigned as "feminine." For example, you've got to be tough, athletic, physically and emotionally "strong" (meaning you don't complain, like ever), and you can't be empathic, nurturing, expressive of your feelings, etc.
And how you really see this enforced is how the worst insult you can throw at a man is to compare him to a woman, and by effect anything feminine. It's about reminding everyone that women are inferior to men, so don't be like a woman in any way or else you're "less of a man" and therefore inferior too.
Have you ever seen that movie "The Sandlot?" Well there's a scene where our protagonist boys are being harassed by another sportsball team, and the captains are throwing insults back and forth. They each seem to be shrugging things off, until one boy crosses the line by saying "You play sportsball like a girl!" and that's too much ... and a challenge must be made (to prove their "manliness" by winning at sports)
You see similar things all the time everywhere ... "You cry like a little girl," etc. Or you'll see drill sergeant types calling their trainees "girls" or "ladies" as a way of telling them they're too soft and really need to work harder, as a motivator because you don't want to be seen as female in any way! When you see a male character in a work of fiction not be the greatest hero, or God forbid see a woman outperform him, men will say he's been "emasculated," because he's let masculinity down and not proven its superiority to femininity ... and that's what all those haters of things like Captain Marvel or current Star Wars are all about (even if they don't realize it)
Toxic masculinity hurts men by forcing you to act a certain way, and not be emotionally healthy.
But it hurts all women, because it creates a culture where it's universally accepted that women aren't as capable as men. Why would you trust a woman to do something instead of a man? She's weak and doesn't have those "superior" traits, so you need a man to do it. If you're a woman trying to make it in this "man's world," you'll run up against barriers all the time because of this, when you're considered the worst thing to be in our society.
Call a man whatever names you want, just never,
ever call him a woman! And that's toxic masculinity in a nutshell
Additionally ... I keep seeing you making comments about how you're "left-leaning," and here calling yourself a feminist, while to be perfectly honest your posting history here doesn't suggest either to me. I feel, based on what I've seen you write here, you'd fit in pretty solidly as a conservative Republican in the United States, you'd clearly be on the right side of our political spectrum. Do you feel you need to keep saying those things because deep down you know you're not, but wish you were? I feel if you want to be progressive leaning, a first step I'd recommend would be to recognize that your current views are anything but, and then learn from others who really are progressives and feminists so you can become what you want to be