You can just change things! That's the power of open source. But for a lot of people, it might seem like a theoretical power. Can you really change, say, Chrome? Well, yes!
We've made a micro fork of Chromium for Omarchy (our new 37signals Linux distribution). Just to add one feature needed for live theming. And now it's released as a package anyone can install on any flavor of Arch using the AUR (Arch User Repository).
There are no speed limits in open source. Nobody to ask for permission. You have the code, so you can make the change. All you need is skill and will (and maybe, if you need someone else to do it for you, a $5,000 incentive 😄).