The reason it's good is because, although it is bad, you never have to worry about it in terms of maintenance, admin or scale. It's like lambda for databases.
For the same price, you can run a much more capable PSQL instance with way better features, but now you're on the hook for it being up 24/7.
You do have to worry about scale with lambda though. It’s not super hard to hit a rate limit where warm up times start being a real problem.
They should really call it "data-structures as a service" rather than a database, really. Programming against it always reminds me of Leetcode problems, having to define your columns in a way to suit the very specific lookup patterns that they allow for.