Why not edit the modules you deem as tagged inappropriately with what you think is the correct tag and serve the community while helping yourself? For instance, I find that Maths is primarily an Envelope Generator and not a Utility module, so you can clearly see that our points of view on what the main Function of a module is might differ.
That being said, as I replied on your FB post, the question that tagging needs to answer to is whether a module can be used as X or not. If the answer is yes, then the tag should/could be applied. Do not forget that some manufacturers tend to overstate what their modules contain and might also overtag just for marketing purposes; I have no concrete examples of their MO but I have seen some examples of overtagging when a module cannot actually offer such functionality. I simple edit on my part solved that but it's not always possible, especially if a Manufacturer decides to lock the module's description, as is their prerogative.
One easy and immediate solution to this problem would be to limit the tag option down to 2-3 tags at maximum. No exceptions. That would force uploaders/manufacturers to really have to decide what type of Function each module serves and by which tag it is best described. Does that mean that some modules would be underserved or underrepresented in particular categories? By all means, yes, that would be the case, especially for modules that have a million functions (I'm thinking Maths or Sports Modulator as good examples of that), but in my opinion that is a small price to pay to make MG cleaner.
We could add a multifuntional tag as a representative of that particular category. A "well, it does more than that" type of thing.
But then again, I prefer clarity. Someone might disagree.