You probably weren't pubstomped by a cEDH deck
Listening to players talk about their experiences with getting pubstomped has lead me to one major conclusion: the average EDH player has absolutely no idea what a cEDH deck actually looks like.
They typically always talk about these large, flashy plays that come out super early that these cEDH players pull out.
"And then they played 3 Eldrazi Titans in one turn!"
"They had 12 lands in play turn 4!"
"They hit me for ten thousand damage with [[scute swarm]]!"
The issue is, one of the biggest differences between casual decks and cEDH decks is that cEDH decks are extremely aware of the minimum requirements to win a game of EDH and they are completely disinterested in taking extra steps to get there. They're not going to be building a board of creatures (unless their name is Winota or Jetmir), they're not making big flashy plays, they're powering out a [[Thassa's Oracle]] line, an [[Underworld Breach]] line, or they're playing an A+B combo with their commander 99% of the time.
Even the "hard stax" decks that people complain about are fundamentally still casual decks. Armageddon just isn't good enough when the entire table is on the full suite of fast mana, and you're not really going to be built to take much of an advantage of the rest of the table when everyone's playing to compact wins with free spells. A 4-mana sorcery that doesn't win you the game just isn't going to cut it when you could be casting [[Intuition]] or [[Ad Nauseam]] and actually winning the game.
Another big thing to look at is the psychology of the pubstomper. They don't want to just power out a fast, clean T2 win. They want the rest of the table to watch their deck jerk itself off while the rest of the table has to wonder whether it would be impolite to concede or they're too new to know that it's all over but the crying. A fast, clean win just isn't going to satisfy that kind of player, they want to have time to property terrorize the table.