I own several replicas and real branded bikes, also have borrowed from friends and ridden the real thing that my replica is trying to copy. My experience is pretty recent so I believe I can comment on a few common topics:
1. the million dollar question, is replica safe to ride?
There is no simple answer for this actually, it depends. If your aliexpress replica is only $200 USD including handlebar, you tell me, do you think it is safe to ride?
However I can confidently tell you if you are buying a $600+ USD replica, there won't be any major safety issues, it is not like you ride your replica normally and it snapped in half immediately, unless you are a heavy rider, but I am pretty sure even branded bikes aren't gonna be that safe if you are heavy, because physics, you cannot have something that is light enough yet still be able to withstand a tremendous load.
I got a friend who has a real Time frame and the front fork snapped in half when he was descending down a hill, spent a month or two in the hospital, he was like 90kg I think? So yeah, famous brand doesn't guarantee safety, or maybe just bad luck, who knows, good thing is Time gave him a replacement for free so if you buy legit that's your advantage.
2. Is replica going to be as good as the real thing performance wise?
Absolutely not, but is it close? I would say yes, replica tends to feel less stiff, a bit heavier and a little bit sluggish. If I really need to give a direct comparison, I will say replica has 90% of the performance, in fact, we all sort of know the answer, if you get dropped, problem's on you, not the bike. Honestly if you are not a racer, don't bother, I don't really think a racer would consider buying replica anyway.
This is not intended to be mean or judgemental, so I hope we can take this response in the sprit of open discussion.
RE #1: Anecdata like this isn't helpful, and to me, the bigger question is whether or not the factory is even testing these frames for safety and failure. If you work with a reputable Chinese factory, they generate a surprising amount of data via testing in rigs to understand fatigue and lower the odds of a frame-breaking. Is the result a guarantee that a product won't break? No. But it does mean that the failure modes are known, and the probability of a frame-breaking meets the ISO standards. Not collecting the data means that it wasn't considered. This is similar to the arguments for and against helmets. Using a helmet provides a data-backed way to mitigate the consequences of an event. Still, there is no direct way to measure the risk faced on an individual ride if you choose not to wear a helmet and you can convince yourself that other factors might make it safer to not wear one.
RE #2: Nearly any race bike frame equipped with similar modern components will be 90% as good as a WT level super bike. Use electronic shifting, use similar wheels and tires, match the contact points and I think its near impossible to find a 10% difference in overall peformance.
I've had the pleasure of riding an Emonda ALR and a Gen 8 Madone now. Even as a smaller rider where the frame matters more as a percentage of aero or weight or whatever, there was no way to look at my ride data and tell the difference between the alloy not aero bike and the WT race bike. You take that from 20-22mph to like 28mph, and yes, there is now a measurable difference, but it's not even 5% and still within the error of my ability to test things on a loop.
How much time and money are you spending trying to make your replica work? How much cheaper does it really end up than something like the Emonda ALR?
Does the extra clout gained from a fake replica do anything for you? I don't think anyone on any group ride will care about this, and if they do, honestly, they are jerks.
If you are saying that a replica bike does no harm because you wouldn't be buying the real thing anyway, what do you do when you move on from the frame? Just throw it away? I suspect that the fakes I have seen being passed off as the real thing often started their life with the first reseller saying, "hey this isnt a real Pinarello" (or other brand), and the second reseller either forgot or isn't enough of a bike person to realize that other people can tell the difference on inspection.
Edit: I want to clarify that I think troll bikes are hilarious—like the LTK bike badged as a "Tractor," for example—but these aren't replicas or counterfeit bikes.