Windrunner entry into service reported as 2027 by SimpleFlying (which I have no trust in). The other two for 2030 according to their would-be makers.
Paper airplanes are easy. Hundreds of them have come and gone over the last decades.
All the other steps are hard - really hard.
Raising the necessary capital (10's of billions of dollars)
Engineering the thing with all the issues that entails, building and flying prototypes.
Demonstrating it meets the design requirements, testing it (including destructive testing for structural soundness) - and all the other stuff needed to get the thing certified.
Figuring out how much you need to sell it for to make it economically feasible (selling airliners at a loss is not a sustainable business plan).
Convincing customers to buy the thing - at a price that is more than what it's going to cost.
Developing a worldwide support network to keep the things flying.
Raise billions more when all that stuff goes over budget.
Bombardier tried to do that with the C-Series. For all intensive purposes it put them out of the commercial airliner business and they had to
give the program to Airbus.
Lockheed tried to do that with the L1011 Tristar. It put them (and Rolls Royce) into bankruptcy, requiring sizable government bailouts and put Lockheed out of the commercial aircraft business.
Sukhoi tried with the Superjet 100 - they've so far lost a fortune and managed to deliver barely 200 of them over 15 years since cert (barely over 1/month - way less than breakeven)
Get the idea?