Chytil is 21. At that age, Ryan Callahan hadn't made his debut yet and wouldn't be a regular for another year or two. The same is true of Brandon Dubinsky, A.A., and Derek Stepan. The problem isn't that the Rangers screwed up the re-build--it's that you aren't giving these kids the time they need to finish developing. The early returns are significantly better than they were in years past. You literally have to go back to the early 90s teams to see the same level of high end young talent coming through the pipeline.
The re-build kind of started with the 2017 draft (where we didn't have much outside of the two first rounders--our next pick didn't come until round 4). It kicked off in earnest in 2018. Two of our three first rounders that year are in Wheeler's top 40 prospects league wide this year (the list that just came out, and includes players from the 2020 draft). The jury is out on the rest of the picks, but there have been positive signs for Pajuniemi. Regarding last year's draft, all three of our 2nd/3rd rounders had great showings in their D+1 years (Robertson, Hendricksson, Jones), and they turned one of their 1st rounders into Trouba.
Rebuilds don't happen overnight. They acquired the youth, but you need to give it time to develop. Chytil is likely set to take a big step this year or next. He's just the first of many, if you give them the time.