They are, and it's specifically because the format never allows (or, perhaps more importantly, never _requires_) the participants to get into real detail about anything ever. It's all just talking points. The opposition never has the chance to actually ask questions that might potentially lead to a situation where someone has to say, "gee, I hadn't thought about that, that's a good point, it will take some careful consideration".
Given the format the only game-theoretical move that makes sense is to employ Arthur Finkelstein style tactics and simply attack the other person, get people scared of them and the world they'll perhaps create, and/or demoralize people that might have voted for them and get them to stay home instead.
This needs to change. Why can't the debate be a day-long event, where they sit down and have serious conversations, not rhetoric but a real dialectic with one another?
I suspect it would reveal a tremendous lack of depth and understanding on _both_ sides. Any cognitive decline, any lack of awareness about world issues, etc. would be exposed immediately. That would pop the bubble, for sure.
Remember the 2016 debates, Trump's strategy is to basically spew as much shit as possible until something sticks - the press will not challenge that except in a few cases (The recent two disaster interviews).
"No puppet, No puppet, You're the puppet" would've been eviscerated in a British election debate (and ours are awful)
There may be a place for actual political discussion between the two sides, but expecting two warring politicians to do so publicly just before an election is not going to happen.