Season one was fantastic, the rest were passable.
Season one has fantastically created the dream 80s atmosphere. The elements such as the unknown lingering evil, the kids, the mysterious girl, all contribute to a well made show by Netflix. The visuals are beautiful, the characters are lively, distinguishable and likable, and the antagonists are scary, both the human and supernatural elements.
For season 2, 3 and 4
Netflix may have tried to replicate the same magic, but we're lost in fan service for season 2. It felt underwhelming, there were barely any new characters, and the ones introduced like Max were tasteless and boring.
Season 3 and 4 were a little better, though they got a little bit ambitious. Season 4 had a good build to the final villain but had an extremely underwhelming finale, sacrificing the new character that had potential to grow, and having the kids save the world yet another day.
Hopefully Netflix will deliver a better season 5.