you actually have to know a bit of everything(at least the main plans) to play e4 correctly
Yes, but a 500 rated player doesn't have to to play e4 correctly. Following opening principles, avoiding obvious blunders and punishing obvious blunders - these are more than enough.
Just cause you know the ideas doesn't mean you play it correctly obviously you'll blunder in the opening half the time
who cares let him memorize openings