Indeed, last-minute Eurostar fares are extraordinarily expensive. But for someone planning ahead, it's still by far the better option.
You don't have to haul yourself all the way out to any of the airports, nor back in from the other. So already, that lessens your time significantly from taking a plane.
The "airport-style screening," I find, is not as bad on Eurostar as a plane because there are no liquid restrictions - I can take whatever toiletries I want in whatever size I want and don't have to separate out liquids into a plastic baggie. Not to mention I can take a friend a bottle of Champagne without paying to check a bag.
The waiting area Is crowded, yes, but I would still rather be waiting in the heart of the city than out at Roissy.
You have to get there 45 minutes to an hour before departure, yes, but that is still less time than you have to be at an airport before an international flight.
And finally, the electric train is so much better for the environment than flying.
I am sorry you didn't enjoy your experience, but I would really encourage people to continue considering Eurostar - to me it is such a much more pleasant experience. And significantly better for our planet.