While dominant oppressive systems remain in place, there is always going to be difficulty removing them. But starting small is always a great start. You can do it on a small scale, by reading the works of LGBT authors, writing to them to show your support, and also writing to the publishers! While writing to Marvel may sound terrifying, and you may not think your voice will be heard, there is always a possibility that it will.
Another thing you can do, that is one of the most terrifying if I’m being honest, is become a writer or artist yourself. If you’re LGBT, and you love superheroes, and you feel like you can write or draw even a little bit, what’s stopping you? Fear. Or a myriad of other emotions. But like Captain Marvel said (who is probably bisexual, honestly):
Below are some resources that you as a fan, potential comic creator, or working comic creator can use for further perusal.