Some supermarket brands are made by the same factories as the original ones, the difference is mostly marketing.
By the way, this is similar to Amazon analyzing the most profitable products from their partner merchants and creating their own "basic" version to take the market. But people don't seem as scandalized when supermarket do it.
I'm guessing you're French based on your instance. I had a friend many moons ago that worked at a processing plant where they packaged the William Saurin stuff (cassoulet, etc). At some point during the batch process once they reached the quota for the branded batch, they literally just switched the label roll to the Lidl ones and kept going with the exact same food.
Of course there's no way to really know which products are like this and which are made with nasty cheap ingredients.
Because once you get off Lemmy/Reddit the world is just fine with white labeling.
If a company takes it's time to build a brand I can trust the product I am perfectly happy paying a little extra. Wegmans does this heavily but in their boxes they have clear and consistent gf labeling. I'm happy to pay a bit extra.
The problem with brands is you have to know the brand to know if you're paying for quality or advertising, or both. There are plenty of big brand name products that are not worth the price, but there are plenty that where the price premium is reflected in the quality of the product.
Unfortunately everything has to be on a case by case basis. I generally favour generics but there are a few branded products that I will go out of my way to buy.
A treat example is Pyrex. It used to be a mark of quality due to the material they used to make their plates bowls etc. Then I got sold to some big conglomerate and they switched to cheaper less heat proof material. Now Pyrex is just a shitty legacy name slapped on crap, but at a premium price.
This is the same for a majority of brand names historically considered "premium" (tools, electronics, etc). The brand gets bought explicitly to bleed it dry by aggressively cost cutting and outsourcing to make a massive short term gain; until enough people learn the brand has been poisoned and raped.
Good brands such as Costco (Kirkland) and Wegmans here do that work for you and well. I've never had a product that was noticeably expensive without the value.