This only works in theory, because it is obvious it does not work in practice at any scale. What if tomorrow Firefox does a major code refactor and your patch b

This only works in theory, because it is obvious it does not work in practice at any scale. What if tomorrow Firefox does a major code refactor and your patch breaks? Would you be able to fix and rewrite it in a reasonable amount of time (i.e. hours) with no knowledge, experience and insight into Firefox's development process? Only full-time Firefox devs can keep an updated fork with their patches, or people paid to do so. That's the point. It's such a massive effort you can do only where and when strictly necessary. There are hundreds open-source project I interact with every single day.