Code quality is very subjective. It's often hard to tell if you're doing a good job. Yes, you may be able to deliver on time, or even have a low bug count, which is great! But even code that performs can still be a nightmare once you pop the hood.

You may be able to update the code yourself without issue. But to me, the simplest metric for if you're doing things right is whether someone else can easily jump in and add a feature. Ultimately getting your codebase to that state is a solid strategy, and then things like automated testing, code linting, reviews, conventions etc... are all tactics that lead to the goal.

If someone else can effortlessly update your code then it's easier to staff up in a time of need (or maybe you just want to go on vacation without feeling guilty).

The biggest problem is that we always tell ourselves, "I'll fix it later". But I guarantee later never comes. Code quality should be a continuous process. So go ahead, delete that commented out code that's cluttering things up, setup an extra unit test, or just rewrite some code that's inconsistent. A little effort each day goes a long way over time.