In all fairness, Groome was a high school pick and has less than 65 innings pitched in pro ball. His not being a top 20 prospect at this age and point in his career is not necessarily a ding on DD's record.
CJ Chatham was the 51st pick in 2016. Not many of those rise to the top 100 in less than 2 years.
The 2017 draft is too recent to judge. Sure, some draftees from 2017 made the top 100, but I'm not sure how many lower picks made the list.
I'm cautiously optimistic about our picks over the last two years, but your point is well taken. Nobody has jumped out as being something very special in a limited time period. Maybe someone will this season, but I doubt we come anywhere near as strong as our farm was 2-3 years ago for quite some time.