James Vaughan's solitary strike 10 minutes after the interval moved Huddersfield six points clear of the relegation zone and ensured manager Mark Robins toasted his first win since taking charge.
Dyche's side, without a win in six, failed to find the net for the third successive match as Danny Ings, Charlie Austin, Sam Vokes and Keith Treacy all squandered good chances.
And Dyche said: "I'm disappointed more than frustrated. It's a very poor performance, simple as that. Unacceptable.
"I didn't think the effort was lacking, but we talk about working hard - we also talk about working smart - and we didn't work smart.
"There were too many players who looked confused with their performance. We came away from the basic principles of what we've been doing."
When asked if securing one of the four play-off spots was now a bridge too far after Burnley slipped into the bottom half of the table, Dyche added: "It's out of our hands now, it's in other people's hands.
"The only thing we can assure is we need to improve on that, we need to go hard because there's enough games to make it.
"But it's a big challenge now because those are the games you have to be winning."
