Lets break this one apart, shall we?
"Zero testers outside the playerbase", but there is still an active playerbase large enough to get testing information back. Testers for a game of this size in alpha traditionally would be few enough to count on one hand.
"Best testers were the PvP players" who would find exploits, defend those exploits as their "right", wouldn't actually REPORT those exploits to Schine, and would fight tooth and nail to prevent anyone else from getting them closed. All the while crashing servers with exploits like docked hulls when they came loose.
"Word of mouth and its all bad" from people who claimed to love the game and got themselves banned, and are now going full on sour grapes trying to destroy it out of some petty need for revenge?
They devs already said they are intentionally not trying to advertise, and that the plan is to start advertising in earnest once the Universe update is done and they stabilize things enough to go to actual Beta. The answer to "how do we revive this game" is pretty simple, IMO. We don't do anything. We are just bug testers with early access, nothing more. What will "revive" the game is when actual advertising starts and we start getting actual new people in by the droves.
I mean, I appreciate the thought, but there literally is nothing we as players can do about it right now, because that ball is not in our court.