Good TV shows come from great characters and a plot that can be sustained for a relatively long time. Both of these are The Good Place's strengths. All the main characters are distinct and idiosyncratic, and most importantly, Eleanor's character arc is very believable (it needs to be so the plot itself becomes believable). Added to this is Ted Danson, who, as always, steals each scene. It's a great combination of characters that works for the entire 4 seasons.
As for the plot, it's anything but predictable. That doesn't always make it good, but it always makes it interesting. It's often bonkers, often excessive, but often creative and sometimes daring. It's not top shelf intellectual stuff, but you have to use your noodle a little bit, which is a lot more that passes for usual TV shows. In short, it's a hoot.