Then the MCU should be littered with Stark like tech, Erskine super soldiers and adamantium laced skeletons. And DCU cops shold all have Wayne tech utility belts and planes should be made of Nth metal.
Some of those are justifiable. Bonding adamantium to bone would kill any subject without a healing factor, for one thing. And Nth metal is alien, so it's probably very scarce. But yes, it is kind of implausible that Wayne and Stark invent all these crimefighting innovations and don't let anyone else use them to fight crime. (Although Iron Man did address that decades ago with the "Armor Wars" storyline, where Tony was outraged about his tech being used for evil and went crazy trying to confiscate it from everyone, good or bad.)
Anyway, I don't see why this is even a debate. Ralph Dibny was on the missing list from the accelerator explosion in season 1. Within the show's universe, his origin is already taken care of, as long as the writers remember their own continuity. All that needs to be explained is where he's been for the past 3 years.