Though it's speculation, I would assign the probability of evolution continuing to work (and improve) on the human race as pretty high -what gain does the human species have in preserving humans from the 21st century indefinitely, when 23rd century or later humans are better?

Getting from "cryonics might interfere with natural selection" to "cryonics is bad" requires crossing a large inferential distance, with plenty of caveats along the way. Evolution has its own ideas about what is better, and they are often things that humanity would consider worse. Genetic engineering might replace evolution entirely.

Overall, in no way can I think of cryonics benefiting anyone other than the individual's (I think simply genetic) desire to avoid death (maybe it benefits future anthropologists I guess), and the cost of cryonics, given that, is what turns me off so much.

This argument is valid - money spent on cryonics might be better spent on charity. But it isn't valid at all price points. For example, if cryonics cost only $100, then even the small benefit to future anthropologists would be worth it. And the cost gets cheaper as time passes and technology improves, so eventually it will be cheap enough to be worth it; the only question is, how cheap is cheap enough?