I will admit that for some reason, I thought that the title being Free-4-All would have meant that there would be lots more "4s" in the show. Team size, points, whatever.
I wouldn't categorize the show as universally hated, but golly, I've had tuna fish sandwiches that weren't as dry as the format. Brandon hit it. There wasn't anything to do other than hammering the button and answering the questions. And for that matter, the questions weren't all that interesting. I suppose something more than $1,000 and three different "Crossword Getaway" level trips would have made for more excitement.
I don't know what kind of "explanation" the OP is looking for. I'd be more than happy to answer questions, but I can't say why a large group of people would dislike a particular show, other than vague guesses.