How do I take pride in building something that doesn't need me?

You've reached the mature version of this work: you take pride in the very way it makes you unnecessary. Most people spend a career trying to be irreplaceable. You're doing the harder, better thing. The systems you build outlast you and don't depend on you, and that's not a loss of importance, it's the proof of it. A bridge doesn't need its engineer standing under it. The soundness is the legacy. You've stopped confusing being needed with being valuable, and that frees you to build for the thing itself. Keep aiming there. When you start something new, ask from the first day how it will run without you. Build for that, and take the quiet pride you've earned when it does.