Difficulty balance is especially hard for puzzle games, I guess. You can get a good estimate with lots of testing (ha!) with many participants, but even then you or me personally can be outliers.

I guess something Portal 2 lacked was the element of surprise.

it ain’t stupid if it works

I’d say that Portal 2 even improved the first one in every aspect.

I personally consider Disco Elysium very much a game (a way better role-playing gamer than most), because an “interactive story” is a game. Combat shouldn’t be a necessary condition. Planescape: Torment should have had the guts to scrap its lackluster combat and focus on its strengths.