Whoops, can’t edit comments, etc. My input is that earlier games were shorter which meant the more difficult levels ended up being more compact and closer to each other in the game’s linear scale. Games today either don’t require the most challenging aspects of themselves or the more difficult levels are just spaced out a lot more since the games tend to be longer.
ex: GameA (from, say, 1985) has 12 levels with 4 of them being notoriously hard. There’s about two hours total gameplay.
GameB (2009) has 15 hours worth of gameplay with 4 hard levels you MUST complete. There could even be more challening levels and stuff, but they’re optional.
They have about the same content of challenging stuff only the earlier game is shorter and thus the ratio of difficult content is higher.