As long as you avoid the UPFs I don't think Aldi/Lidl can do you too wrong. Some of their imitation brand UPFs are atrocious in both quality and nutrition, but frankly even most branded products are also awful these days and have plummeted in quality while hiking costs that they should be avoided anyway... Although Aldi's imitation Pepsi Max/Lemon & Red Fanta are the real deal and both supermarkets' energy drinks taste like Citrus Sharp Polos which is very nostalgic
Meats are standard for a supermarket and are no worse than the other big supermarkets and a lot cheaper, but the chicken breasts stand out as exceptionally bad and are pumped with so much water that you end up boiling them when it floods out and don't seem to freeze too well and are always very tough when defrosted. But we already know you don't go to a supermarket for quality meat -
that's what butchers are for and it will cost you a premium.
Fruit & veg are good, usually a bit cheaper but as a whole last a day or two less than the other supermarkets which doesn't really matter anyway. I can't comment on the bakery or general bread quality - we bake our own stuff.
I like both, at the end of the day they're not really any worse than the others and the price at the till is noticeably lower. We've all learned what's great and what to avoid in there by now, right?