Just look at this link on Quora asking about 'When someone makes money in the stock market, must someone else be losing money?'[1]. Almost every single answer there disagreeing with that question about stocks you could swap stocks for crypto and it'd apply equally.
Also anything a business creates also has a real world cost as well. If not with your cash (but it often is, with subsidies, tax breaks, loopholes, or other things), then with the business' impact on the environment, their effects on laws that affect you (i.e. Disney extending copyright law), or just consuming resources that you could have consumed for less if they weren't creating a higher demand for them. If everything was in homeostasis, then not a big deal, but we haven't been anywhere near that for a long time.
And yes, I'm aware bitcoin isn't great for the environment considering how much energy it currently consumes for mining. I don't like that either. That doesn't make it a scam or a grift though.
[1] https://www.quora.com/If-someone-is-making-money-is-someone-...
