When I was a child in the 90ies, older people still called Aldi "Albrecht" (and the middle class avoided going there for fear of being marked poor):
https://upload.wikimedia.org/wikipedia/commons/0/04/Albrecht...
https://upload.wikimedia.org/wikipedia/commons/1/13/Aldi-Kal...
https://www.lebensmittelzeitung.net/news/media/7/The-Albre-b...
Interesting side note: Aldi is not called Aldi in Austria (it's "Hofer" there, which blew my mind as a kid since the logo is the same), because the Aldi trademark belonged to "Adel Lebensmittel Diskont" there.
At least in larger cities, the average Lidl often looks a bit run-down and grimy, and the customers tend to be lower class (that's not the case in rural areas, however). I always found that interesting, because prices / quality are basically equivalent (although I tend to prefer Aldi products). I live near the border to France, and the situation there appears to be similar.
At least a few years ago, however, Aldis in Switzerland also looked very run-down (though not as run-down as Denner) with distinctly lower-class customers and a much larger focus on selling alcohol than in Germany.
[0] https://www.augsburger-allgemeine.de/wirtschaft/Bilderstreck...
However (I've lived some years in FR and PL too), nothing beats Dutch supermarkets in terms of shopping-speed. Nowhere. If you think (German) Aldi is fast, you should try a Dutch shop (preferably in the city around rush hour so you can see it shines under pressure). As a low anchor, you can try the same in France (any brand, but Lidl too) ;) This includes stock: Dutch supermarkets are rarely out of something, but in Germany this is par for the course (or I am extremely unlucky?)
Also, and this is actually quite true for the Netherlands as well, there is a quality problem. It can be good, but it rarely is great. The French (and Belgians) really have that beat, at the cost of speed. Only fresh veg and bread is where Lidl shines, and I love them for it.
I've given up on them. And almost anything else too. Because that is a function of modern bakery supply chains in general, not one specific 'outlet'.
Do not get in a bad-bread-pissing contest: Dutch will win it every time.
Anyway, I remember the talks about that fear of being marked poor. It was all a load of BS as you could see from the parked cars, and style of clothing of shoppers.
Similar to BILD.de perceived as trash-tabloid, nonetheless having the largest circulation.