That's true, depending on what you're looking for though. I've noticed a handful of brands that tend to hold value really well, and some that don't.
I ended up buying new because I wanted something very specific and the used prices weren't far off new, and I looked for months daily at a bunch of different sources (craigslist, fb marketplace, offerup, etc).
But there are definitely great deals out there. All depends on what you're looking for...budget, what you're going to use it for, features, etc. Length, weight, stability, budget, etc are all important considerations.
Paddling around a calm lake for exercise and fun vs a stable boat you can stand up and sight cast from with lots of storage vs something you want to paddle for long distances are all very different things, with boats vs their own advantages and disadvantages. The important thing is figuring out how you think you'll use it, then finding a good match of those features inside your budget.
One general piece of advice...don't skimp out on the paddle. That's as important as the boat itself. And learn some decent technique. Do that, and you'll have a much more pleasant experience. If you have a good shop around you, see if there's an opportunity to take some different equipment out for demos before buying.