Governance of the project.

How you make decisions, long term goals, short term goals, what features you decide to add to your app, what if any marketing you do, and so on.

When a project is small, you might think that governance is unnecessary, everything is obvious. Then the project grows, more people come in, there are disagreements, different points of view, perhaps even malicious actors, and you don't have a working system in place to resolve all that, a system for making decisions.

From what you've said, Fdroid is making mistakes. But there is no way for you to influence them to fix the mistakes. They have bad governance. The bigger the project, the less you need to think about technical details (because you'll have other devs to do it) and the more you have to think about big picture items, including good ways to make decisions.