How did Shakespeares plays and poems become thought of for only highbrow intellectuals?
The Puritans came along and decided that plays were immoral because the theatre was immoral. After recovering from that blow in the Restoration, people were in the mood for topical comedies that satirized the high and mighty. Gradually spoken English drifted further and further from Shakespearean English. English has lost a great many of the prepositional phrases in use during Shakespeare’s life, as well as the use of reflexive verbs. Words like ‘nosegay’ became replaced by more current words like ‘bouquet’, and there were a lot of these. In short unless you see the play being performed, the vocabulary is a stretch.