That said, I'm not certain that engineers are in a different situation. Judging by videos I've seen of collapsing buildings and other issues, I wouldn't be surprised if structural, electrical, plumbing, and other engineers also hand over their designs in the beginning, and then leave it to the developer / contractor to interpret them and 'value-engineer' as they see fit.
when i visited beijing about 10 years ago, i was astonished at how much construction was going on, and i could see that the sheer amount of construction happening would make it seem like there were more issues than here in the US. without more concrete data, i'd be skeptical of that kind of anecdote simply playing into our own biases.
In the US architectural process, an architect specifies a particular material (say a roof sealant) that has certain characteristics. During construction, the contractor will look at the material, check its price, and then use their suppliers to see what the best available deal is. The contractor identifies another roof sealant that's half the price. Because they've bid on the project for a fixed price, if they can use that other product and cut their costs, they'll increase their profit margin. So they put in a change request and submit the new product with its data. The architect may review it, see that it is functionally the same as their specified product, and approve it. Or they may look at it and determine that while they're both roof sealants, the specified one has a 10 year lifespan, and the proposed alternate has a 2 year lifespan. They reject it, and the builder uses the specified material.
Without the architect verifying that the material is comparable, the contractor (intentionally or not) will use a lower-quality material that will lessen the quality of the building, because there are no checks in place.
His greatest frustration was the lack of quality in the finished buildings he'd design. As he put it, the designs that Chinese firms were putting out were just as high quality as anything in the rest of the world, but the end result was always worse. It was largely procedural -- in the US, the architect is involved not only during the initial design phases, but throughout the project, and is responsible approving any changes and for certifying that the result matches the intent. In China, that's not the case -- they make a design, bundle it up, and then hand everything over the contractor. The contractor then makes whatever changes they want during the construction process, without any input from the architects. This means materials may get changed, the wrong construction methods may be used, etc, and no-one knows. From a distance, the building will look amazing, but the details will have been skimped on.