IMHO, even if it were a zero-sum game *overall*, it absolutely is not the case that a newb is getting taken advantage of on any particular trade. I'm sure others can come up with better examples, but off the top of my head.... Let's say somebody owned a put he had bought as a hedge (say, SPX Jun18 '20 2700), and he was perfectly happy with his purchase and with his continued ownership, but he doesn't need the hedge any longer (we don't need to know Why). And let's say he's one of 25,000 owners of the exact same put (so there're 24,999 other back-stories behind why they own that particular put). And then somebody, perhaps a new options trader, decides to sell a bull put credit spread because he's bullish; so, for example, he sells 2725 and buys 2700. And coincidentally, at the exact same time, the seller sells to one market maker, and the buyer buys from a different market maker (and neither mm is being "taken advantage of", as they're watching their greeks quite closely). So, did the newbie get taken advantage of with his purchase of the 2700 put? Nope.
@stinkypants