>Yoda spent upwards of 800 years as a Jedi Master, teaching many generations of Jedi Knights. Through those years, he had unlimited access to the vast Library in the Jedi Temple on Coruscant, with all the books, artifacts, and holocrons the Order had accumulated over the millennia. He spent centuries learning from and teaching some of the greatest Jedi Masters of all time.

 

>Luke did not have access to any of this knowledge. He was forced into action after mere months of informal training under an old and dying master, and spent a large amount of his career scouring the galaxy for fragments of Jedi lore that Palpatine missed in the purge. Despite his best efforts, he could hardly have recovered more than a tiny fraction of the knowledge that was lost. The finer points of dueling were lost with the masters that knew them; those that could have mentored him in the classic forms were either killed in the Clone Wars and the Purge (Form II, Dooku; Form VII, Windu) or died before they had the chance to teach him more than the basics (Form III, Kenobi; Form IV, Yoda). Force Lighting, an attack Luke struggled to defend against for most of his career, was obviously not a problem for Jedi Masters before the purge; Yoda and Windu are both shown redirecting it without taking damage - Yoda doing so with his bare hands.

 

>The Library was destroyed shortly before Luke's birth, and he struggled all his life to attain the basic knowledge that a few months in it's halls could have given him.

 

>Yoda's Force abilities were naturally great, but were also highly trained over centuries with all the knowledge of the Order at his disposal.

 

>Luke learned most of his abilities by instinct or by experimentation; his development was hindered by his lack of training. Many of the abilities he learned, such as generating Force Storms, he learned from his enemies.

>Yoda mastered all of the lightsaber fighting forms, learning them in the mature, polished form that 3000 years of combat use had given; and he used those forms effectively against many enemies who were also trained to a high level.

Luke learned the basics, and learned the rest by trial and error; mostly against backwater foes and rustic Sith Lord - wannabes. The few times in his early career that he faced against a truly formidable opponent, he either lost or required back-up to win. As good as he eventually got, its clear he never quite made it into Yoda's league.