Y'know that thing where Spotify is on shuffle but refuses to play certain songs in your playlist? And you can shuffle the same playlist several times over the course of a week and it'll seem to have "favourites"? Yeah, it isn't just you; this is a real thing and it's stupid. Gabbi has put together a great video essay on why (to the best of their knowledge) this happens and provides some (frankly) common sense suggestions that I deeply hope Spotify hear, take on board, and enact.
tl;dw: Truly random shuffling is annoying, because it creates artist clusters and disjointed play styles, so Spotify binned it. But it seems that they've overengineered it in the other direction (I mean, do you remember when shuffle on Spotify would occasionally catch you off guard with a track combo that just worked but made no sense? That doesn't seem to happen anymore!), and now factor in idiotic metrics like artist popularity and how often you've listened to a track, creating a recursive loop where the algorithm consistently reinforces its own bad guesses. This shouldn't be surprising; they made the same mistake with the weekly "for you" playlists, where these slowly become more and more focused around the kind of music that (you guessed it) they had been recommending for the past couple of months. Still annoying though, and Gabbi's suggestion of keeping most of that stuff but seeding the playlist with a truly random starting point just seems so obvious to me as a fix that it's baffling how a company with the data, money, and talent that Spotify has doesn't just, y'know, do that.