Oh come on! They're software developers! The code they wrote three years ago is total shit and you (we) know it, haha.
Take the time to learn something new, today. It's practically what makes a software developer a software developer. If you're not learning a new language, engine, or technique pretty regularly you're going to have a hard time (eventually).
The reason why software developers reinvent the wheel so often is because we know that the old wheel is garbage. It at least, the way we used it was. After being a software dev for a few decades, looking at your old code should always give you a feeling of, "I could've done that better."