People who purposeful avoid gluten just because they heard it was bad for you, do it in an uneducated manner. Those who have to for health reasons at least (for the most part) get some education on what happens when they avoid all those foods.
They are too-often ending up with low fiber diets because they start avoiding all fiber-rich foods, and don’t replace that fiber with other sources, low folic acid because they’re avoiding vitamin-enriched foods and not taking, or not taking appropriate supplements or not getting it from other food sources. So from this perspective, it’s not the lack of gluten that’s the problem, it’s the lack of education on what avoiding those foods really means from a nutritional perspective. But given that it seems most people don’t know about nutrition anyway, they don’t know what they don’t know.
I’ve seen a couple of studies (all overseas IIRC) which hint at the possibility that totally avoiding gluten, without a medical need, has an adverse effect on the health of the microbiome. Some of this has to do with how a lot of gluten-free “grain” products are made, using tapioca, potato starch, rice flour, which don’t have a lot of the nutrients that grains have, aren’t fortified, and can be fairly high in sugar and starch. It’s like the fat-free craze which resulted in far too many people over-consuming carbs and sugar.
Gluten is not inherently good for you, either. So avoiding it is not a bad decision. I do, and I also avoid sugar. Not because I have any inherent sugar problem either, but I know that a diet too high in gluten or sugar is inherently bad.
ETA: we may just be talking about different issues here. I don’t buy many “gluten free” foods that normally have gluten (e.g. cookies, pasta, etc.) I do try to avoid additional gluten for no good reason - in salad dressing, in mayonnaise or cold cuts, etc. Then again, I don’t tend to buy many premade items at all because I don’t want a lot of the crap that is in them.
Yes, the issue is that too many people eat not just way too many carbs, but way too many carbs from refined and highly processed grains, which are devoid of naturally occurring nutrients and fiber.
Just because a diet is high in gluten and is “bad” for you, doesn’t mean a diet that includes gluten is bad. There is some evidence that some level of gluten is healthy for the gut microbiome as well as helping boost the immune system or lower triglycerides No, those are not huge studies, or over long periods of time, but they do suggest that there are indeed health benefits of some level of gluten
The problem is when it’s excessive, and that may not even be about the gluten itself, but what comes along with things that contain gluten. Some whole grains in the diet are fine. Tons is not. Processed grains in foods that tend to be high in sugar and starch is not healthy when consumed in excess. Gluten gets the blame far too often 