Splatoon 2 won't be out for 6-7 months so plenty of time to fix up some things. We go through this every year. Wonderful 101 blocky characters..few months later blocky characters gone. Xenoblade X shown at E3 2015 and a month before release new video shows many improvements including an entire mountain range not there before.
What people don't get is a demo of a game still in development is an old build already. The demo you saw is maybe a 1-2 month old build. Don't get upset til we are upon release.