AliExpress is a marketplace, same as Amazon or
Ebay. Like both those platforms there are reputable brands and traders and some less so. There are also degrees of protection available if you know how to use them.
My advice is:
* Buy Choice whereever you can - you get the most protection and the fastest delivery
* Stick to the bigger AliExpress brands that people vouch for on Chinertown or other Forums. I would happily recommend ZTTO, IIIpro, Ryet, Goldix, Spedao as trusted parts brands I have personally bought; YKYW, SpExcel and Darevie for clothes; Toopre and Risk for tools. This doesn't mean every product is good... it just means that they have a brand name that has been going for a while they try to protect
* If you are buying anything 'original' like Shimano there are good prices available but only ever use highly trusted traders like Anracee or Yiwu Donglue - never anyone unnamed or with low feedback
* Never buy anything counterfeit, ever
I don't get the 'moral, exploitation and safety grounds' argument. A massive % of stuff you can buy is made in China even if it has a mainstream Western brand on it. Reputable traders selling via Choice have brand names to protect and need to comply with the legislation in the jurisdiction they are selling in (e.g. you can't get flashing lights if you set your country as Germany.) And much of the same stuff is available on Amazon, which arguably is an even less moral place to buy.
Also in connection to another earlier comment prices under £135 always include taxes and tariffs, so you will never be stung for customs.