First, after a while of taking it you do not notice the taste. I have taken it for 17 years, in rotation with other antibiotics.
Second, you do not eat it like candy or a cough drop. You do not leave it on your tongue. It needs to be taken with liquid and it should spend a millisecond on your tongue as you rip back a power swig and then power swallow it with a flavored beverage. Once you learn to do this, you will not have issues or at least less issues with the taste. You are only tasting it, in all likelihood, because you are not getting it down right. It cannot be done namby pamby, you have to power it down.
Third, it is medicine, not candy. Medicine is not supposed to taste good.
Fourth, in my 40 years with IBD, I have been forced to eat or imbibe many things that are more vile tasting than flagyl. Flagyl might not even be in the top 10 most vile tasting substances I have had. If you think flagyl is gross, try drinking liquid potassium some time if you want to taste some really vile crap.