No one denies that King Lear has a plot. No one really holds that against Shakespeare. If too many contemporary plays are being written with a disregard for storytelling that's too bad for us and for them. Exploring the possibilities of the stage is hard for me to look down on, until that becomes as institutionalized as whatever commercial form is ignoring those possibilities. If this has happened of plotlessness, it happened when I wasn't looking.
Hat Tip: LRN