I think it is important to know what type of item you are buying on aliexpress. All of the stationery sticky notes and tapes I have bought have arrived so far. The other thing that I bought was clothes, and there had been only one issue with the seller when I bought a pair of pants and it didn't match my size. Aliexpress sellers will fight you tooth and nail against refunds. And usually the site itself is on the sellers side. But it was my fault for buying the wrong size. The other clothing had arrived with no problem.
Just remember that you buy what you pay for. If the item is considerably cheaper, then either the quality is bad or the seller wants to scam you. I had bought a pair of pants for around 40$ and the quality was extremely good. But again, it depends on the seller you are buying from. Items the same price can have different quality.
Some of the sellers don't respond to my messages and questions about the item, or they say something else entirely which is probably done with an automated system.
Overall, aliexpress is an okay site when it comes to buying clothes (just look at the sizing info and measurements when buying) and cheap stationery. I have no information about the potential safety of other types of items nor have I buyed any.