Every young player develops at there own pace. For some players, like Clelin Ferrell, it can take some time at the NFL level before they start playing like a fourth overall selection. While some can have an immediate impact, it is not always the case for high draft picks.
Take a look at Raiders 2018 first-round pick Kolton Miller, the team's starting left tackle through his first two seasons in the NFL. It took him a full year and an offseason, which including him gaining almost 20 pounds of muscle. No developmental pace is the same for any two players.