People do have bad taste, and even they often can't stand their own preferences after a while. This is one reason why "popular" music changes constantly. If you want to know what is really good, it is only really easy to tell after it has stood the test of time (say, 100 years to be sure, but a bit less can sometimes be okay, but certainly no less than 50 years). Thus, Bach, Mozart, and Beethoven may be judged to be really good, as they are generally considered to be good after more than 100 years. Louis Armstrong has held up well for over 80 years (for some of his early great performances found
here), so we may include him in the category of easy to determine to be really good. (None of this is to suggest that something new cannot be good; the point is, it is easier to tell that something is really good after it has stood the test of time. Bach, Mozart, Beethoven, and Armstrong were all really good when new.)
As for new things, most of it sucks. This, however, has been true for many years, and possibly forever. Often, people pick something because it is new and different in some way, rather than because it is actually good.
And some people have such appallingly bad taste that they still cling to crap after pretty much everyone else has given up on it and judges it to be crap. Some of this is driven by nostalgia, but it is still bad taste regardless of the motive. The nostalgia motive dies with the people who grew up with it, which, again, suggests that the test of time must be about what I said above to be reliable. That some old fart likes what he or she grew up with proves nothing about its real value.