I don't think L4 autonomy is a pipe dream. Indeed, it exists today and is widely available in the same city you drove your Tesla in. I think it's a pipe dream for Tesla specifically to achieve it, because for bizarre and idiosyncratic reasons Elon Musk won't let them use LiDAR or mount a roof sensor. They've been stuck at L2 for a decade now, and I don't see much reason to think that making that system incrementally more reliable will ever "unlock" L4.