I particularly hate UI changes. There seems to be a constant trend in phone software to "improve" UI while disregarding the value of consistency and familiarity. Sure UI can be improved but if it's not a massive improvement the negatives of relearning the UI and retraining muscles memory far outweigh the positives. Same applies to features too, though often due to the UI changes that come with those features (Android Chrome's bullshit tab groups pushed me to Firefox).