I’m not trying to “poo-poo” on linear regressions. This post was the product of a PhD student (a PhD!) trying to do a linear regression on data that was was clearly not linear. (Something like the example with caloric intake and activity.) It was more of an “epistle” to them to be careful because, had that analysis plan made it to their academic advisor, it would have shown a lack of care in the exploratory data analysis. But yeah, with proper use and interpretation, linear regression is useful.