Even though Boeing (BA) had good years in the past, I think it's a good example of a sector to avoid:
1- A very competitive industry (mostly airlines, but Boeing is directly related to airlines);
2- No or very low competitive advantages (I'm talking about airlines, once again);
3- A catastrophe with a plane could cause a lot of harm to a company, like it was the case with two 737 MAX (two accidents with more than 350 deaths);
4- A sector related to the general state of economy;
5- A sector where companies are usually heavily leveraged (high debt);
6- A sector with low margins.
Of course, Boeing is better than Bombardier which is Quebec's turd. We're certainly not talking about Couche-Tard here. But even if Boeing is better than Bombardier, it's not an easy sector at all. For instance, Boeing now has liquidities problem. And the dividend will probably be suspended for some time.
Mines, oil, gas, airlines (and all the industry around it) are the hard way to make money in the market. Always been, always will be. I'm not a prophet. I only write what I've read 15 years ago and what's still true.
At the opposite, with Ross Stores (ROST), you've got a company that sells clothes at a discount price. You won't see a lot of effect of the economy there. And you surely won't see any scandal either.
With BA, you've got a stock which is at the same price today as it was 6 years ago.
With ROST, you've got a stock that's now selling for 2,5 times the price it was 6 years ago.