The majority of the items we list today, we can trace them back directly to the distributor. We have blacklisted some selling websites based on low customer reviews.
FWIW, I had a long conversation with an ex-enginner who switched to selling European furniture in the US. He described European factories building steel-reinforced furniture on one shift for the European market, then on another shift flimsier too-thin-wood-reinforced versions for the US market.
One easy hack can be to look from the bottom into e.g. a new sofa and reinforce sections which appear likely to sag over time.