In defense, Chinese manufacturers have a lot of work to do in terms of communication, marketing, etc. I am always surprised to see videos of frames coming out of the back of a workshop at some manufacturers and resellers, with just a sheet in the background in a more or less dirty setting. Then, we can see machines dropping weights to see the strength of the carbon. In short, there is a little artisanal side that is not very reassuring.
The communication is a big one. On my Epic Evo clone frame there was a big defect where the derailleur housing and brake hose routing holes in the front and rear triangle didnt align near the BB so you couldn't even build the frame up. I had to use a dremel and widen the routing holes in the front triangle to get things to align. Communicating with the seller was a lost cause, they just said they'd tell the factory and ghosted me.
My AirWolf Stumpjumper clone had bad threads in the front triangle main pivot. Torquing them to over 5nm just shredded the threads in the front triangle (they came from the factory at 2nm at best). Frame was unridable without those bolts torqued properly. I had to buy a helicoil kit and install my own threads, then source my own bolts, because AirWolf refused to help me. Yeah they sent me new bolts one time but it wasn't a bolt issue, it was a front triangle issue. I provided video evidence showing the issue but they just ghosted me.
And in each instance the frame was $750-850. We're not talking about $200 frames where defects are whatever, these are fairly expensive. As a matter of fact, last year I was able to get a 2023 Specialized Stumpjumper carbon frame for $650, A 2023 Stumpjumper Evo frame for $750, and a 2023 Specialized Enduro frame for $800. All brand new with lifetime warranty. Those frames are significantly better quality, have more features, and cost the same amount as these clones.
Yes, I know that pricing was lower than most sale prices at the time, but it was a sale through The Pros Closet. And many other frames can be had for similar sale prices if you wait and dig enough.
My point is that these frames aren't inexpensive. And depending on the time of year the pricing isn't really even competitive with more reputable brands. So when issues do happen and the seller ghosts you leaving you with a $700+ headache its not a small wonder people go online to complain about them. All bike companies have issues, if you hit up the Specialized board on the MTBR forums you'll find plenty of people complaining about Specialized. The difference is that Specialized sells significantly more bikes so issues are more likely to be one-offs, their support is actually accessible, and they won't tell you to pound sand if you actually find a manufacturing defect.