12-20 days usually only applies when you are sourcing products from places like China. If you are in the U.S. and are sourcing from a U.S. manufacturer, most ship the same day and customers have their orders in 1-5 days.

If you are using the AliExpress dropshipping model, 12-20 days is pretty normal and that is only if you use ePacket. If you use any other shipping method, count on it taking even longer!

If you make the shipping time abundantly clear on your website, there are usually no problems. The biggest problem with the Ali-dropshipping model is that there is usually a TON of competition for those same products, which is why you really need them to be impulse buy items that people don't think about too much or do a ton of price shopping for.

Mixed feelings? Loser mentality. How did you go into this without figuring out where you are sourcing your products and what your terms are?
That should have been number 1 on your list of priorities.

There are a myriad of places to source from. You can even walk into a local goods store and buy the product at x cost and sell it on your ecom store at y cost (factor in taxes and shipping). Alibaba/express/bigbuy/ebay aren't the only places.

It is not a problem at all (especially when you notify your customers about that)

[DELETED]