Just a correction on one of your implications. Temu has free returns, which includes shipping costs. For low cost items, they will often do no return refunds too (which may be good or bad, as then you have to figure out what to do with it, but you got your money back).
With the quality of Amazon taking a five over the last few years and trouble returning things (a lot more trouble than TeMu), I have found that cheaper generic items are better from TeMu (and branded items are probably better from the supplier, where responsibility can't be shifted around and the people earning the money are the ones provided the product).
And as far as getting those unbranded or off brand things goes, I have actually done quite well on temu. If you actually start looking for something different than Amazon instead of the same but cheaper, there's quite a lot that you really couldn't find on "americanized" shopping sites.
I'm not saying TeMu is great. I have had things arrive broken, smelling strongly and unpleasantly of plastic processing, clothes that had pockets rip in a few wears and lots of things that were certainly not ever going to look as good as in the shop image photoshopped onto some huge buff model... but
there is also a consideration of what the alternatives are. Not everything is available from local charity thrift shops, and at some point at least a certain class of items makes more sense to get on TeMu, where you can at least pretty easily get an "item didn't match description" refund.