Oat Milk, even the very best, is syrupy and thick. I think most people looking for a latte without dairy are better off seeing the Milk Alternative’s flavors as their own thing rather than trying to replicate a dairy latte. There are a lot of upsides to be found if you stop chasing an impossible goal.
Notably, I found that a Soy London Fog is actually single-handedly a better drink than a milk London Fog...but it is different and if you are chasing a milk product you won’t find it.