anywhere remotely interesting to visit is packed from dawn to dusk

That's a bit of an exaggeration, I've been having the time of my life here in vietnam, just ask the locals for some ideas and check Google maps for traffic to avoid the one everyone is already going to, and you'll have a beach, mountain, beautiful twisty roads along rivers and mountains, local swimming hole, etc to yourself and like 3 or 4 locals who you have to flee before they invite you to lunch, introduce the whole family, then dinner, then to sleep at their place, marry their daughter, etc.

Its not an issue of too many people, just everyone goes to the same exact place because some influencer recommended it.