Personally, I think 'lack of confidence' is just another excuse. It's been 3 years now. 3 years.
Burisleif (who hasn't been around for a long time) kept going on and on and on and on about, how change takes time. 3 years. Is that time enough?
Anyhoo, even if Caroline is low on confidence, it's her responsibility to fokking do something about it. Hire a coach ... Nah, scratch that. Been there, done that, saw the movie and bought the t-shirt.
Hire a sports psychologist ... Now there's a thought. But as she hasn't (as far as we know), she probably doesn't see confidence as that big a deal.
IMHO it's technical deficiencies, notably on the FH wing. When a player cannot hit 3 FH rally shots in a row without netting the ball, its a technical deficiency rather than lack of confidence. Again imho of course.
Her backhand also can make errors in key moments. Her forehand is still the side that can really fall apart. Also her serve is not reliable at the end of close sets.
Yet she's made 2 semis and a quarter in her last 4 tournaments and all 4 losses were to good players:
Venus when she had her best week, Li (current #2), close match with Ana. The weak loss was to Jankovic in California.
When those are your last 4 tournaments, it doesnt seem as far away as when Muguruza & Wickmayer are beating her in early rounds.
So the next step is to keep getting through draws to play former #1's or #2's on clay. Dont have excuses. Fight for these matches. That will also help confidence, if she can win matches on clay with nothing to defend