Must it be argued? Is it too juvenile and unserious to celebrate it?
No, but I would say that the issue is a complex one that includes philosophical matters that are not easily settled. That said, by the most widely-used measures of standard of living, I believe that they are increasing overall. However, consider this as a complexity:
My wife recently met with an old friend in Dalian China at a bar. She had to take a picture of the menu after having a long discussion with the bartender. I will have to ask her for the specific numbers, but I recall that he made something like 2400 ($384) yuan every month working 7 days a week. Yet that was his base pay. Some of his wages were usually garnished as his boss often fined him for infractions such as allowing too many cigarette butts to accumulate in the ash tray. He pointed to a table and said: "Those three people have already drank $1000." That drink on the menu listed for 6880 CNY is $1100. He couldn't find better work. In fact, people would line up for his job.
There is something uniquely dispiriting about being a servant of wealthy humans that seem fundamentally equivalent, and seeing no out. This is one anecdote, but the situation is shared for many Chinese. I believe that socioeconomic arguments must consider these measures when determining a standard of living. Humans are complex social creatures. We can have all the wealth in the world and live in torment. We need to be clear about what our goals are.
No doubt, the standard of living has increased globally by many measures. What I wonder, is could it be increased in a more humane way? And, dare I ask: Could it be increased more quickly in a more humane way?