I don't quite agree.  It's more than a disclaimer. It does actually represent the way GDP and similar data points are used in the field and in professional advice to policymakers and business people. GDP per capita is a very good way of measuring economic growth, and its use in the field is mostly limited to discussions of economic growth.  It is not a particularly good way to measure economic well-being and usually isn't used as the primary evidence regarding discussions of well-being -- unemployment or other data points are used instead or with GDP. For example, GDP is but one of the frequently published and cited economic leading indicators which are meant to summarize both growth and well-being aspects of the economy.  All of the indicators get reported; not just GDP alone.

However, it cannot be denied that there is a strong association between economic well-being of even the poorest sectors of a society and GDP, regardless of how it is measured, particularly when GDP growth is slow or negative, so it would be dishonest to eliminate discussions of GDP from issues of well-being entirely.

I just don't see many economists doing the things you attribute to them. I do see a lot of other people doing it, and I see economists frequently and publicly correcting them when they do. (I just came from the right of center National Association of Business Economists annual meeting, and entire sessions, as usual, were devoted to precisely the topic of the misuse of GDP in policy debate and how to try to correct it.)  It's just not the field's fault. It really is the journalists here.