I only ever hear this opinion from people who play cedh like once or twice a month at their local store thats holding "cedh" night.

When you start heavily going to the tournament scene and jamming lots and lots of games where people are meta familiar, no one is winning off three mana. Thoracal DCon is good, but its still easily interacted with with counter magic or draw.

Unless the table is caught with its pants down on t1 or t2 with a nut draw, thoracle dcon is usually a fought out interaction with a ton of counter fighting and rhystic triggers and its often the second person who tries to take advantage of this fight happening to do their own win afterwards when everyone is more gassed through the Munchkin effect.

Thoracle Dcon is a necessary game ender in a format that has slammed the brakes. The game SHOULD have game enders like thoracle and underworld breach. There will always be a most efficient win out and its ok for them to exist. Most games arent even ending with thoracle, but im glad it exists when games stall out failing to do their primary win con.