[2023] Has 7 days become less interesting to watch streamers play?

It's 100% that most of them have played and replayed and rereplayed and rerererererererererererereplayed the game over the years... They know every little thing about the game and have long fallen into the trap of familiar patterns, They've been involved with 7DTD for so long that they know the best builds and for most people choosing to do something that is not the objectively best method is hard for them.. Jawoodle and GNS are a rarity in that they do try new things quite often in their base building, but even there they test it out and minmax it, there's no on-the-fly 'will this even work?' suspense. You know, because of who they are, that they've tried it out and it WILL work.

Like you point out OP, the player gets to choose the difficulty, and which biome to inhabit. Higher-risk biomes offer higher rewards (How else would you want it?). Similarly, which POI to enter, and when to restart a game entirely, is up to the player.

Since all these things are in the player’s control, it seems to me it’s up to the streamer to figure out what is interesting for their audience. We can debate which of these choices are more or less interesting to watch, but surely the game isn’t at fault when a streamer opts for a less interesting choice. If watching someone encounter the unknown, that doesn’t know what they’re doing, is more interesting, then find a streamer that’s newer to the game.