Many people use GDP to make claims about changes in people's welfare over time. This is entirely reasonable, and would likely be correlated with any reasonable measure of people's welfare. It is not, however, perfect, and it will miss things.
It is not, however, perfect, and it will miss things. First, it often does not include many things which we might find valuable, such as leisure, life expectancy, total population, and household production, and may not track onto utility if there is inequality and non-linear utility as a function of wealth. Second, GDP cannot adequately capture the gains to utility from free goods, in particular the Internet.
Second, GDP cannot adequately capture the gains to utility from free goods, in particular the Internet. Relatedly, goods with markups will not be able to state. Third, the way in which we treat investment arbitrarily increases GDP in places with higher capital intensities.