How to handle the erasure of your 'digital legacy'?

I've been struggling with something for a while now and ironically a sitcom from the 80's finally helped me pinpoint the problem. My TV was on for background noise and I noticed that it was an episode of Family Ties. In the episode, Elyse Keaton was having a problem. A prominent building that she designed was being torn down and replaced by a cookie cutter mini-mall. She was struggling with her "legacy" - her mark on the world - disappearing. After the building was gone, what evidence would there be that Elyse Keaton was there?

I'm facing a similar issue. I don't like getting into my day job too much online (for various reasons), but suffice it to say that applications that I developed for decades are being sunset/replaced. I've developed quite a lot over the decades, but eventually it would all be replaced. Once it is, what will I have as "proof that TechyDad was here"?

How do you handle the existential crisis of our works being digital and transient versus having an actual, physical product?