I agree with many of the points above, you should definitely not use Iron Router, use NPM not packages, Blaze is alive but if you don’t like it, sure go on to React.
But I disagree with this: “What I do know is our ambitions of where we want to take our platform are growing faster than the framework’s offering every release.” Seems more emotional than factual. Which ambition was held back? Were you planning to land on Mars? The starting premise is important for the value of article and it’s unsubstantiated.
So you replaced Meteor with Express, React, Redux, MobX, Apollo, Webpack, Passport, and a few others (focusing on core functionality only). So you now have to worry about all these packages getting maintained (including SECURITY!) and their compatibility. Seems like your risk just shot up. Way up.