I know it's not an ideal food and at best, something that should be used sparingly. But is it a good/decent alternative to traditional flours for someone who is trying to gain or maintain weight?
No doubt it's carby, but if you're in the Safe Carbs Are Good camp you could count them toward that allowance.
Functionally, rice flour is an excellent substitute for wheat flour in things sich as gravy. Without the guten or toxins of wheat. In fact, sauces thickened with rice flour freeze better than wheat or corstarch thickened sauces. Look for Boxes of Mochiko in the oriental section of the grocery store.
I use rice flour for baked goods in addition to potato flour/starch and tapioca flour/starch.
For thickening the starch products work wonderfully but my preference is using pureed vegetables for soups, stews, etc.
I don't actually eat any of my baked goods, yeah I know but they have other outlets, the last round of pineapple orange muffins that I made using only the rice flour were a huge hit and the response was "these are the first gluten-free anything that I haven't wanted to throw at the wall." So they're tasty.
Just depends what you want to use the flours for. I totally agree that these aren't food, I'd rather have steak, potatoes and braised kale, but if you need an option on occasion I think they're great.
If you want to gain/maintain weight? Go the route of tuberville or if you're not eating tubers for some reason try adding in some winter squashes, carrots, beets, parsnips, bananas, cottage cheese..