Reason number one is shipping and attitudes regarding small orders. I have seen detailed videos about how things we buy on Aliexpress go from start to finish into our hands. Sellers are not honest about who they are and how well they operate. A seller can be a factory or distributor who nine out of ten times sells on Aliexpress one item at a time but hates it because they would love to just sell 1,000 pieces at a time and just do large orders, but thought oh well let's do this too even though we hate it. They barely care about one single cheaper or smaller item getting to you on time. Also, depending on where they are in China and how busy they are, your package may take a few days just to get from their warehouse to the local shipping center! Oh, by a few days I mean to say up to 5 or more. That is downright unacceptable. Sometimes these packages are moved by small, slow vehicles through congested traffic and based on what I've seen it's a miracle they even get to the local shipping center. This all stems from the fact that Chinese logistics infrastructure is nowhere near what it takes to make China not just the factory of the world, but also the dropshipping supplier for all online stores of the world. People, there is a reason why we still buy goods that have been imported to our continent by other companies and sold to us through online retailers and local stores. They take on the risk of sourcing, negotiating shipping deadlines and quality control, making it available to us locally within reasonable time frames and so on. When you buy direct from China, YOU TAKE ON ALL THOSE TASKS AND YOU HAVE WAY LESS NEGOTIATING POWER THAN A LARGE RETAILER OR IMPORTER! Still think all of this is worth a lower price? Might I suggest asking your boss for a promotion or a raise so you don't have to deal with it? Seriously, even a side gig will help boost the finances to avoid Aliexpress altogether.
Reason number two is that the level of Aliexpress seller dishonesty is more than I can handle. Clothing sizing issues, lies about jewelry materials, product quality misrepresentation and much more. One thing is to do great marketing and PR and present yourself in the best possible light. Another thing altogether, especially in e-commerce, is to seriously mislead your customers and under-deliver to the point where you won't get repeat customers or any good reviews at all.
Reason number three is that Aliexpress prices are going up. The sellers on there have been looking at what American and Canadian online stores are doing with their goods. They looked at product descriptions, keywords, private label to make products cost more, and so on. So many times I saw an Aliexpress seller take a pair of sunglasses from one of the Chinese factories, slap their own private label on them, and charge way more than the price of the exact same sunglasses if bought generic from the factory seller or a standard distributor. The best of the best items in any category are no longer that much cheaper than buying them locally. Add to that the long shipping time and the whole idea of buying from Aliexpress is not that attractive any more.
I'm sure that if you shopped on it and had similar experiences, you could list a few more reasons. Personally, those are my three biggest ones. My advice on how not to need Aliexpress and the headache it brings is simple. Be clear on what you need and stick with it- don't go over. Hand pick what you want to buy so you get the best items for your money that were carefully picked, imported and come with shipping and product quality guarantees, as well as clear return and exchange policies. If you still decide to buy things on Aliexpress here and there, especially clothing or electronics, be prepared there's a good chance you'll lose your money, or at least a portion of it. If this sounds too harsh, that's because you haven't shopped on there much yet ;)