Gelato disappointingly icy
That recipe has a pretty low butterfat content and no real stabilizers, plus a lot of water. Commercial gelato is usually made with low butterfat also but with a lot of stabilizer, sometimes several different kinds. Although gelatin isn't usually used, you can think of how it affects liquid, and stabilizers sort of do the same to compensate for the lack of butterfat. Gelato is also not usually frozen hard, but rather served at a warmer temperature because it generally doesn't freeze well.
I made gelato once by starting with a commercial mix that had stabilizers included, and it came out great. But most of the home recipes I see for gelato either turn out like yours did, or they're really just ice cream recipes with lots of whipping cream but they're calling it gelato -- which they can do, because unlike ice cream, gelato has no regulation as to what percentage of butterfat is required.
If you really want to make gelato, I'd suggest trying to buy a commercial mix, or experiment with stabilizers such as xanthan gum powder.