Cardano was already designed with sustainability in mind. The point was to create a system that governs and also finances itself without being dependent on donations. Cardano has a built-in treasury system that gets a constant stream of funds from transaction fees and treasury taxes. This is explained in detail in treasuries with Bingsheng Zhang.
Cardano Improvement Proposal
Cardano Improvement Proposals (CIPs) are a way of formally proposing ideas in an agreed-upon fashion. While nothing about them is binding and not a pre-requisite for either treasury on protocol changes, they fulfill an essential aspect of Cardano governance. Before a decision can be made on anything, someone has to propose a setup that others can discuss.
Fund your project with Project Catalyst
Project Catalyst, Cardano's innovation platform is the current way to access the funds of the treasury system. It is seen as a stepping stone to Voltaire and aims to provide a safe and lively environment to explore the highest potential of human collaboration.