Firstly, quantum computing at scale _might_ be possible in our universe but it might not. One of the spookiest things that might still be true would be a thing called finite non-local hidden state. In this scenario the whole universe has some sort of hidden state, a bit like the seed value of a Minecraft world. Quantum computing in a universe with finite non-local hidden state just weirdly "doesn't work" when you scale it up, because it's basically using the universe's hidden state as magic working storage, and that runs out. Simulation nuts would tell you finite non-local hidden state makes it pretty clear we're in a simulation, but then they would say say that...

Secondly it says "near future". We have every reason to believe there will be serious obstacles to scaling up quantum computing. Somebody else gave the example of Babbage's engine. Just because we can conceive of fusion power generation doesn't mean it's going to happen next week.

Or at all. At the start of the 20th century some mathematicians thought all of mathematics could be formulated as a handful of assumptions plus a huge chain of inference. It was just a matter of writing it out precisely. Surely an inevitability. This project was begun by mathematicians and philosophers and it was going pretty well (proving that 1+1=2 for example) up until this chap Gödel comes along and straight up proves it's impossible with his Incompleteness Theorem, if you can do 1+1=2 then Gödel shows how you can write out effectively the equivalent of "This statement is false" and blow up your whole system.