How to generate ideas?

Something I’ve always struggled with is coming up with ideas on my own. This is nothing new, it’s a problem shared by many millions of people around the world. I’ve tried several methods for creating ideas, none of them have been particularly successful for me. I’ve tried random sentence generators, stream of consciousness writing, mediation, you name it. What’s more is that I haven’t been able to find any way to consistently come up with good ideas. For instance, I run an Etsy store where I sell Print-on-Demand t-shirts. I’ve published hundreds of products and only had one or two perform really well. So how do I replicate this? I’ve tried creating similar products in the same vein as the originals and they didn’t sell nearly as well. Heck, the same designs on different products (hoodies for example) didn’t sell nearly as well as the shirts. So is the context in which an idea is delivered just as important as the idea itself? It would seem so. I’ll continue to come up with bad ideas, it seems to be the only way to get to the good ones.