I actually disagree with the point about factories screwing up on purpose. If you have worked with Chinese suppliers you will surely know that consistency is not a word you can use. Sometimes they send you a batch with certain specs, sometimes is off. Sometimes you found they don't send you anything because, well, because the factory has closed, or they decided that they would manufacture doorknobs instead of watch springs. Well, this is what replica factories deal with on a daily basis. Take a look at a Regmariner (which is essentially a Noob v5) and put it side by side with a v9 Noob, it's just night and day, mate. Better crystal, better steel machining, the insert!, better dial, etc. Hell, even the bracelet is better on a V9 compared to a V5 (and Noob bracelets are 100% subpar).
There IS an improvement, but you need to look in longer intervals. As you very rightly say, there's a new model every few months, so you can't expect a completely new watch. But check what we had 2 years ago and it's way better now. And then check what we had FIVE years ago and you'll realise the watches are definitely improving.