I don't recall there ever being complaints that the vocal tracks in song lessons were too loud but this is one of a half-dozen or so complaints (mine included) that the new balance is way too low.
To be clear, the so-called balance is a fairly recent change in the wrong direction. In this case, GT has fixed what wasn't broken and It's time to go back to the way it was. That return shouldn't take any time to implement.
"It takes a lot of devotion and work, or maybe I should say play, because if you love it, that's what it amounts to. I haven't found any shortcuts, and I've been looking for a long time."
-- Chet Atkins
-- Chet Atkins