I haven't used Training Peaks since it was a Flash/Flex app. I imagine for a vast majority of Strava's user base, they're not into the detailed micro-management of their workout plans and goals. And they likely aren't athletes working with coaches, etc.

There's been plenty of new app features and user interface updates over the years. I think you're conflating your needs of a highly technical training plan with goals and demographics of the Strava app.

That said, I'm still waiting for Strava, Zwift and Trainer Road to merge into the mega one-stop-shop. ;)

Edit: Also add RideWithGPS to my uber-list of one company, since I use them to generate my route maps over Strava's version, because I think it's better, which actually goes to show that the little guy can still compete. (Probably a small niche market, though.)