You really expect that kind of support from something ahipped across the globe for peanuts? Ali/Temu and the kind serve specific purposes and they do it well.
I find reviews on those sites still useful, and at least on Ali there are a fair number of negative ones as well. Users tell if a specific part works with Home Assistant or zigbee2mqt.
I suggest to sort by order number and not stars.
The "kind of support" they say they expect is the ability to leave a negative review. That doesn't seem too extreme of an expectation honestly. The only reason support came into the picture is that Temu redirected them to support.
"That kind of support" is the absolute bare minimum. If you're not even providing that then you're not fit to sell anything, at any price.
But that is unfair competition against rule-abiding vendors. Platforms like Ali and Temu should face the most strict limitations for that alone.