Training alone isn't what allows riders and teams to reach potential I'd agree with that. If that were the case the teams wouldn't bother employing dozens of additional performance staff working with the coaches, you would simply see a few coaches and doctors like the 90's and 00's teams had and be done with it and save yourself several hundred thousand $ in wages each season to spend on better riders.
There was Pinot last year saying he missed simply being able to go and hang out in the town square relaxing and laughing before starting a stage, saying today they're locked on the bus studying the days race strategy, nutrition plans, data, google maps, veloviewer, warming up, warming down etc etc. Even Froome is saying the same, that the sport is now unrecognisable due to the amount of data being used by the teams to be more competitive, even redefining how a bike race operates today.
I think it all just comes down to evolution and improvements in all areas, nothing significant or identifiable on its own, but when you see the likes of UAE, Jumbo & Ineos with so many staff compared to the 90s, there is obviously a performance gain that has been found doing so.