I believe they've been known to make exceptions and host far larger games than 5gb, if you contact them directly and explain your situation and see if something can be figured out. But by default they give a small filesize limit to avoid everyone uploading huge unity/unreal engine 4 things by default and putting a strain on their servers. Essentially, they want to make sure they're only allowing larger filesize limits to those that need them. And unfortunately, making a large series of ranting posts across the forum will do very little to earn their favour.
I get that you've worked hard on your game, and are upset that you can't upload it at the current time, but these are generally issues you'd want to bring up with itch.io directly via email, as the forums aren't the best place for those that can help you to notice such things.