There is some crypto that we know how to break with a sufficiently large quantum computer [0]. There is some we don't know how to do that to. I might be behind the state of the art here, but when I wasn't we specifically really only knew how to use it to break cryptography that Shor's algorithm breaks.
You are misdirecting and you know it. I don't even need to discredit that paper. Other people have done it for me already.
Recent advances in quantum error correction are a significant increase in confidence that quantum computers are practical.
We can argue about timelines. I suspect it is too early for startups to be raising funds for quantum computers at this stage.
Source: I worked in quantum computing research.