Poorly word on my part, of course you can bulk up.
But you can't make someone 5' 11", become 6' 3" or make some average pace, become rapid.
Take Luke Thomas, he's decent technically but he's never going to have the physicality to be a top level fullback, no matter how hard his trains. You can make marginal gains but not massive changes.
Some things are just genetics, Usain Bolt wasn't just a record breaker because he trained hard, he had the right genetics to make it possible.
Do you think you could coach Jannick to be quicker?
But you can train muscle memory we repartition and coach people to make better decisions. Better decison come with experience and improved understanding.