True and the GM and his scouting department bring in the best talent they can find. Sometimes the coaching staff does a poor job of developing these picks. Sine times the player just doesn't want it bad enough and doesn't put in the work to improve. Sometimes the player gets injured and it shortens his career. And sometimes they just miss. It's hard to know who to pick. These guys play different positions and are playing different competition levels so it's tough. The whole league passed on the GOAT six times before he was picked. London Fletcher went undrafted.
It's an educated guess and it's up to the coaching staff to develop the player and put him in a position to succeed. Snead picked up AD in the middle of the first round and he is already an all time great DT. He got Kupp in the third round. He does a great job.