Many large projects may look like a mess but their success is because they got the high level architecture right and perhaps had the moat of a large tech behemoth behind them.

VSCode, Tensorflow, Kubernetes, Go, Typescript, React. These are a few that come to mind.

At a high level, they are all fantastic projects and perhaps messy in their own way, but they are absolutely fantastic, hardened proven codebases with ~millions of users.