On his Tumblr, an anonymous poster asked Marvel comics writer Jim Zub the question "How did you break into Marvel without kowtowing to their effed-up leftist agenda?". Except he didn't say "effed up".
So Jim Zub answered, and he has allowed Bleeding Cool to run his reply in full.
First off, I think it's important to establish that answering your question doesn't mean I agree with the premise. Marvel Comics (and Marvel Entertainment) are huge corporations employing hundreds of people and run by dozens more. I have no doubt that there are individuals across the political spectrum who work and run Marvel.
I'm being 100% honest with you when I say I have never received any kind of top-down political agenda from my editors or their superiors. The stories I write are generated by me and receive feedback based on the visual and dramatic potential of those stories, and how they may impact other parts of the Marvel Universe. That's it.
As far as I'm aware, any broader themes that come through the stories in Marvel Comics come from the creative individuals building those stories. Agree or disagree, that's the story they're telling, not a huge well organized political conspiracy.
I think the mistake you're making is assuming that Marvel is a singular entity. I know it's easier to visualize a company as one idea (and that's a big part of corporate branding, so I get that) but under that surface is a group of people and, in a more immediate sense, individuals who you build work relationships with.
Bill Rosemann was the Editor of Marvel's Special Project division. They handle advertising and other comic projects outside of the continuity-driven Marvel Universe. He knew of my work, especially my sword & sorcery comic writing, and approached me about the possibility of pitching on Figment, a title under an imprint they were building called Disney Kingdoms. I worked really hard on Figment and proved to him that I could deliver a solid story on spec and on time. As we built up trust on other projects in his division, Bill and I started talking about me making the move over to in-continuity Marvel superhero writing.
Bill ended up getting a promotion and became head of Marvel Games (handling video game and related licensing), which would have left me without a perch at Marvel, except he did me a solid and told all his editorial contacts at the company how hard a worker I was and to work with me if they could. That led to pitches for a few different editors and, eventually, a chance to write Thunderbolts for Tom Brevoort in the Avengers office.
Bill Rosemann gave me a shot after I'd established a consistent body of work and solid reputation. Tom Brevoort gave me a shot after Bill told him I was worth investing in. Two hard-working people who saw potential in my work, not a shadowy cabal with steepled fingers as lightning crashes behind them.
I get it. It's easier to assume a grand interconnected evil thing built with nefarious purpose is trying to keep you out and crush your creative dreams. In my experience and conversations I've had with dozens and dozens of creators, it really isn't.
Do the work, build your skills, explore opportunities as they become available. Rinse and repeat. You won't necessarily achieve everything you dreamed, but you'll make a lot more progress than by hurling loaded questions from behind the veil of anonymity.