do you think: CTL is a lie for fitness, CTL drives fitness, or "it depends".....I think it depends
I don't think it's a lie. It doesn't
drive fitness. Ideally it
reflects fitness. It's fair to say it doesn't tell the whole story. You could do three slow century rides a week (if you had the time), and have a high CTL but low power and VO2. Any single number isn't going to tell the whole story of your capabilities, and whatever system you're using to track fitness needs to strike a balance between detail and comprehensibility in order to be useful to you (I'm looking at you, Golden Cheetah). If I were a coach or pro who was paid to understand all this stuff, I'd put more effort into comprehending all the stats that I'm generating.
there is something to "sweetspot" style methods of training?
This is one of the big debates in training. There's evidence that polarized training gives you a better payoff, but it also seems that it only works if you're investing a lot of time.
is "more is more" true to an extent? why or why not?
No, because if you do five high-intensity workouts a week you'll overtrain or burn out.