Saying there is no punchline when there is no punchline isn't being unfairly cruel or anything. No one is trying to make you feel bad (at least I'm not), but perhaps rely more on jokes with a setup and a punchline. Not all jokes have to have a rigid structure like that, but it works in 4 panel comic strips quite well. A joke isn't "Look at how against type the characters are acting". It would be if someone said something funny, but no one does here. Don't stop drawing or writing, but perhaps take criticism and learn from it.