I very much agree that the ISO-fu'ivla are silly. In addition, I consider them rather useless. When the discussion that spawned their creation came up, I felt it a better idea to go the opposite route: instead of making "cultural fu'ivla" for all the existing X, a list that will continuously change and pretty much always result in words that can only be understood by people who know the ISO in the first place, make lujvo stripped of their specificity. All of the cultural gismu have one or more of six categories in their definitions, hence the creation of the six lujvo {tutra'a} (geography), {selgu'era'a} (nationality), {klura'a} (culture), {jdara'a} (religion), {cemra'a} (community), and {banra'a} (language).
Without going into opinions as to how common talking about such is or will be in Lojban, it is handy to be able to talk about {lo klura'a be lo nunjmaji} or {lo jdara'a be la.vylkan.} without having to look at some arbitrarily long list.