Drafting a QB in 2018?

If Goff doesn't improve next year and looks just as bad. Throwing bad passes, fumbling and stumbling around. Not able to complete critical 3rd down passes. How long will it take to know he is a sure BUST? Do the Rams sticks with a guy who obviously doesn't have the "it" factor for 3 or 5 years like they did with Sam Bradford?

If the Rams get the #1 pick of the 2018 draft.... who would you want to draft? Is Sam Darnold of USC a Andrew Luck type of QB?