I believe that's only true in flat or declining markets. Growth raises all boats, figuratively speaking.

Any time you buy, there's a counterparty selling, and vice versa. If they had not bought or sold on their end, they would have made the money rather than you.

That's all I was trying to say. Obviously this is simplistic and there are many reasons why someone might rationally be fine with being on the losing end- they might have something else better or less-risky to do with their capital, for example, or they might be a market maker that is not interested in holding anything long-term, etc.