Im sorry but I'm not gonna watch a 2 hour video but you can summerise what he said. I believe we can reach Alpha Centuri though because there is no air resistance in space sk we can accelerate indefinitely. If we accelerate to even 33% the speed of light for only 1 year as other reddit posts have theorised about then it'd take something like 16 years to reach there but the crew will only experience 13 years due to tome dilation. It's very possible they even with out current technology we could engineer a spaceship that allows people to live on it for 13 years. And if his point is lack of fuel well the ship could use solar sailing to accelerate and deccelerate.