I've found that my tastes in bicycles is rather cyclical. Sometimes I like friction shifting and 5-6 speed freewheels, sometimes I want indexed integrated shift/brake levers and as many gears as I can get.
I don't get rid of parts that I remove - you can fit the drivetrain from a few bikes into a single shoebox without many issues, and it's pretty easy to switch between modern and vintage components without making permanent changes to a bike.
I do sometimes regret the 650B cantilever conversion on my 716, but I only feel that way right now since I've been loving how fast I am on my Super Le Tour 12.2, "modernized" with 8s Campagnolo Mirage levers and a modern aero-ish lightweight wheelset. Comparatively, as-built the 716 is a heavy, plodding bike but it's time to shine will come soon enough when good full coverage fenders become a welcome feature, and downtube shifters are so much easier to operate when wearing bulky winter gloves.