Long story short: Dragon Quest Builders 2 is shaping up to be just like the original, but with smart new features and quality-of-life improvements. Many of those new features weren't accessible in the demo I played at E3 2019, but you can get a glimpse of them in the trailer below.
According to the producers, the idea behind the original Dragon Quest Builders was to take a sandbox-style building game (i.e. Minecraft) and give it the structure of a, you know, regular video game. It was designed so that anyone, young or old, longtime gamer or novice, could pick up a controller and learn how to build cool stuff. Dragon Quest Builders 2 is based on those same principles, but expands your capabilities.