In praise of Sanitarium (1998)
I played at lot of Sierra games as a kid in the 90s, and only a few adventure games since then. I recently bought Sanitarium on a whim, and it's the first adventure I've ever completed without resorting to a hint book or walkthrough. That felt really good.
It helps that each chapter of the game is rather small and self-contained. And you generally only have one or two items in your inventory at any one time. Only a couple of instances of pixel hunting. There are several "apparatus" puzzles that can be confusing at first, but aren't too bad once you spend a few minutes with them. I wouldn't say the game is "easy" in a bad way, just a bit more logical I guess compared to the adventure games I was used to. (By contrast I loved numerous aspects of Grim Fandango but so many of its puzzles were terrible).