The vintage 2000s aesthetic isn't really one set of effects so much as a combination, and it all depends on the specific photo! Back then some people shot on Kodak with warm glow, others shot on Sony point-and-shoot cameras with a bluish tint, so it's better to start by figuring out which look you're drawn to.
What actually works: warm tones (add yellow to the temperature), slight blur around the edges with a vignette, a bit of grain - the previous answers got that right. But there's one detail people often miss: in the 2000s it was popular to have a light haze, almost like a blur across the entire frame, not just loss of contrast. In Snapseed or Lightroom you do this by lowering clarity or adding a Gaussian blur on a separate layer with low opacity - that way the photo looks like it was slightly "fogged" when you took it.
One more tip: don't overcomplicate it! People often throw all the effects on at once and end up with a mess. Start simple: +warmth, -contrast by 15-20%, light grain. If that's not enough - add a vignette or blur. Look at examples from the internet from 2005-2008 and copy the feeling, not the slider numbers.