Aldi siphons away marketshare from other stores with large overheads and from brands which spend more on advertising than the products themselves. Personally I very rarely notice a difference in quality between Aldi-bought products and those from more expensive chains (e.g. Edeka or Rewe), though the latter are more hit-and-miss (never need to check the expiration date at Aldi, always have to at Edeka…) and much more chaotic. This second aspect, which makes it hard to shop quickly, combines with very slow people working the tills, meaning that the time it takes me to buy a single item in Edeka is longer than what I need to buy a whole week’s worth of food at Aldi.

The random collection of stuff is mostly useless, yes, though there are some items there with sufficient regularity and quality to be worthwhile, e.g. WD-40 and tape. Clothing is typically also ok though neither fashionable nor pretty.