What is a bad advertisement?
Hi,
Good or bad is a qualitative measure, very broad in itself. Good for one can be bad for others or vice versa. Let’s consider the case of following picture.

What would you say about this? In my view, good for the advertiser as he need not to book a full wall for displaying his offers, whereas, for a person walking by this building every day, it may be just a dirty wall with the posters of cheap products. An eyesore. Everything depends on your point of view.
In general, 3 main reasons an advertisement can be considered bad are:
1) It does not meet its intent. For example, a toothpaste advertisement shows an actor jumping off the walls (too random to deliver a message). The other situation can be sending a message to the wrong type of buyer, like trying to sell a comb to a bald person. It must not be forcefully imposing something we don’t want or feel deceived after purchasing it.
2) The content of the advertisement is not acceptable to a group or society. Like, an advertisement promoting prohibited activities.
3) An advertisement with technical glitches such as improper graphics, annoying colors, etc. Anything unpleasant to the eyes.
However, there can be many more reasons if we get specific. In olden days, there used to be less or almost no competition among products. With the growing competition, advertisements have an important role in the success of a business.
Imagine if there were no advertisements at all. I’ve created a little article telling a hypothetical story about what it’d be like if we lived in a world with literally no advertising. I hope it gives some additional insight.
Well, to sum up, I will say there is no empirical yardstick for an advertisement to be good or bad. To make it better, an advertiser should work upon the discussed points as much as possible.
Thanks,
Cleo