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.
3. How's the paint in the replica?
Pretty good, if you don't tell anyone that is a replica I doubt your local club rider is able to tell the difference unless they also have experiecne with replica. However, it is not perfect, you can't really expect a perfect paint with that price if you really know the process & equipment required to get the paint on the frame.
4. You buy replica? SHAME ON YOU
Yes I am a bad person, I own $10k+ USD worth of cameras & lens from Sony yet go cheap on bikes, I have no respect to legit brand, plz don't be like me.
Btw, if you are not a DIY person nor got the time, probably not so wise to buy replica because there are going to be a lot of little things that need your DIY capabilities.