I grew up in a small town in the Lafayette area and I concur with all of your points. I would also add that traditional Cajun food is poor man's food. They're made from low cost ingredients. In some cases, there could be some no-cost ingredients (e.g., if neighbor gives you fresh ducks from their morning hunt).

Probably one of the most divisive ingredients for gumbo is okra. Some will tell you that it's not a real gumbo if it doesn't have okra. The other camp won't eat it if it does contain okra.

On the use of file, I could probably count on 1 hand the number of times I've seen it used. Everyone knows about it, but I've never witnessed it being commonly used.

The two biggest challenges (IMO) of gumbo are the roux (making it without burning/scorching it, in which case you have to throw it out and start over) and the sausage. My family stopped making roux decades ago. They all buy pre-made roux. You can buy it with and without oil. I prefer using the roux without the oil because the jar doesn't need to be refrigerated after opening and it doesn't spoil (plus it's healthier). My family always has used smoked sausage for all gumbo (whether it's chicken, seafood, duck, etc.). Finding fresh smoked sausage to impart the desired flavor is very difficult. The very best (IMO) is the smoked sausage made by Teet's Food Store in Ville Platte.

I'll add on to your comment about the slow cooking. Not only the food should be cooked slow, but the chef should not be in a hurry. In my experience, my best gumbo and jambalaya comes from having plenty of time to cook it at a leisurely pace. Also, my jambalaya is only cooked in big cast iron pots. One of my Cajun cookbooks gives the admonition "Qui va doucettement va surement" (He who goes slowly goes surely).

Dang it, now I'm craving some.