The core problem is that large numbers of people trade for effectively no good reason. Because of HFT, these people are now less screwed than they were previously. The "house" is competitive.

Yes, it's a profitable business for HFT. I'm not too bothered by that.

If you want to direct your ire somewhere, direct it at companies like Robinhood that are gamifying financial markets.

No more zero sum than two parties exchanging one thing for another.