Code clutter is much more consequential than it gets credit for. Poor formatting, inconsistent whitespace, snips of unused code, and misleading filenames are speedbumps (or worse, spike strips!) that a developer is going to hit every time they sit down to code.

And unlike bad abstractions -- which you can "learn" about and mentally model -- the friction of clutter is a constant damping to your productivity.

Building features in a cluttered codebase is like being asked to install plumbing in a hoarder's basement.

Understanding a cluttered codebase is like reading an advanced math textbook by candlelight that was written with broken typewriters by a group of modernist poets.

De-cluttering is the first thing you should do, and you should stick to it above all else. Before you add tooling, before you refactor, before you abstract and framework-ize, get rid of the clutter. That means format your code, and use a linter whose rules are based on widely adopted community conventions.