Good quality coffee should continue to develop in flavor substantially as it cools and is actually quite interesting to taste across the temperature spectrum. I’m sorry that hasn’t been your experience. I do understand coffee is not for everybody, but I do believe if you have the opportunity to experience well prepared craft coffee it has the potential to change that view.
Think of cooling coffee having a similar effect as decanting wine, because high end coffee is actually extremely similar to wine. The fruit is fermented in massive containers in a very similar fashion to wine making, imparting a large volume of complex flavors. The act of roasting coffee is actually one of the most difficult sciences in the culinary world, to the point that Michelin starred chefs want nothing to do with it - it’s actually that difficult to execute well. It is pretty easy for somebody to grab a bag of green coffee and absolutely destroy it. It’s incredibly rare for someone to do a coffee its justice. And even then, if the person preparing it once it is roasted doesn’t know what they are doing, they can take the best coffee in the world and make it taste awful.