Nonsense.
WotC sells hundreds of old D&D PDFs, uses Twitter, Facebook, and Reddit extensively. It produces YouTube and Twitch videos and podcasts constantly. It has a massive online store selling fan based material. It has no problem with the Internet.
Why you can't get 5E PDFs? Because of the retailers, not because WotC is scared of intrawebs.
They have greater retail penetration than any other RPG company on the planet; they also consequently have more distribution restrictions than any other RPG company on the planet.
But, man, WotC does not have a problem with the Internet. Well, most of it.