Most of his bad reviews (both during and for quite a bit after his life) was about how ‘low’ his plays seemed. It was the German Romantics who started the Bardolatry movement.
Any bad review will do, anything to break up the bardolatry (I like that). My sophomore English teacher was really irreverent, he’d tell us which of the literary giants were junkies, he’d pick the weird parts of their catalogs (when it came time for Joyce he had us read An Encounter), made fun of the pie-pan sound effects on the version of Macbeth we watched, fun guy. He’s the only English teacher I had that didn’t ruin stuff, because he didn’t worship it. He respected it, but he knew not to take it too seriously.