Aliexpress is not a seller but platform that provides services for buyers and sellers to conduct transactions.
Buyers are protected its security despite all the sellers are in China. Because the system is a system of payment aliexpress escrow payment order by aliexpress.
So shoping in aliexpress money you are secure because before you receive the goods that you buy, then aliexpress will not make payments to the seller.
In Aliexpress If you do not receive you items within the time promised by the seller, than you can do dispute or request a refund for items not received.
If you are not satisfied with the goods you buy at aliexpress, you can ask for refund, discound or ask exchanged with goods with the desired buyer.