Singers are adding their own notes and flying up and down scales. This hurts my ears because the notes they choose and the scales they sing do not belong to the chords that are written, and do not even follow a chord progression.
Often times, they are also missing the notes, going either flat or sharp just enough to make my ears bleed.
It is also becoming worse because they are slowing the tempo down, drawing out the length of the song, sometimes to almost double its written length. I guess this gives them more time to soar on all the notes they can possibly fit in.
Play the notes and at the tempo the music is written!