The Royals had plenty of players that underachieved in 2019. There are some players that are just never going to be even average players in the majors. And there are those, such as Danny Duffy, that have proven their ability but struggle with issues of health and consistency.
The Royals also have young players for whom it is still too early to know what their ceilings may ultimately be. Nicky Lopez struggled mightily, at times, but he was also only 24 years old. He still has a few more chances before anyone should write him off.