- Almost all Powered by the Apocalypse games
- Almost all Forged in the Dark games
- The 5th Edition World of Darkness games
- Almost all 2d20 games from Modiphius (Conan and Infiniti being the exception)
- Cortex games like Tales of Xadia, Marvel Heroic Roleplay and Smallville
- The Cinematic Unisystem used for Buffy and Angel RPGs
- Into The Odd and Black Hack are profoundly less complex.
After getting rid of my Pathfinder Second Edition books I don't think anything on my shelf is more complex than AD&D, certainly not to run. Maybe Draw Steel, although I find it much easier to run than AD&D or 5e.
AD&D is no Champions or Pathfinder, sure. But in the grand scheme of RPG design I consider it pretty much smack dab in the middle complexity wise