If the semi had been joining a freeway, the Tesla would not have encountered the trailer at the angle it did. Transposing: if full auto-assist use had been restricted to freeways, this 'accident' would not have happened.
The same factors that allow for higher speed limits on freeways make them the only safe place to utilise this technology at this time. We're talking cars and plebs in public spaces here, not $m planes and professional pilots in managed airspace.