First they busted out Hyperglide, and made indexing work. Then they put the shifters where they belong. Then they came up with Di2, and transformed electronic shifting from an expensive curiosity into the state of the art.
Now, it's a fully enclosed gearbox. Before you roll your eyes, there's a twist or two: it uses a derailing chain, and one set of cogs moves laterally to maintain a perfect chainline. So it's lighter and more efficient than spur gears, and very likely to be more efficient than a pristine derailer drivetrain, and certainly more efficient than an even slightly dirty one. Not to mention more aero and far more robust...
Granted, it'll be heavier than a derailer drivetrain, but perhaps not by a huge amount, and it's a good place to concentrate the weight. It should certainly be possible to build a road bike using one of these that weighs less than 6.7kg...
https://www.bikeradar.com/news/shimano-gearbox
Oh yeah, thirteen speeds with a range of 470%.