I know nothing about coding or programming, but I have noticed that there is a wide variety of problems being reported. My issues are relatively minor, just annoying…ridiculous delays when adding a song to a playlist, infrequent jettisoning of a song halfway through playback.
Others have catalogued really egregious problems. The silence from Apple about this is deafening. Some say Apple does not read these community support boards. It seems to me that, if they did, they might ponder what they screwed up that could cause such a varied distribution of diverse problems. There is no shortage of clues from which they could triangulate.
I violated my usual protocol and updated my phone to iOS 18 right away. Once I witnessed my issues, while finding nothing online initially to suggest a problem with iOS 18, but noticing the precise correlation of my issues and the upgrade, I turned off automatic upgrades on my other devices.