Fulfillment business is very hard. Amazon has invested well into the hundreds of billions building it out, and that's supported by their economy of scale of Amazon.com. A fulfillment business for toilet paper would never pencil out profitably no matter how hard you try.

This is actually a great example of the consumer winning out due to Amazon's business. Pre-Amazon, 24 hour shipping was literally not a thing, even 2 day shipping, especially for free, was a major innovation of the site.

So for fulfillment for general goods, I do think this is something that you will never be able to compete with Amazon on as a small player profitably. However, there is plenty of competition in specific verticals, such as Instacart or Doordash for groceries specifically. And if you want to be a toilet paper producer/seller, that is possible too (just not the fulfillment part but again I'm not sure why we expect "toilet paper fulfillment" to be a valid category that needs to be a thing), for example I bought my phone case from Dbrand due to the strength of their product and marketing. As a small player you need to compete on specific verticals but that has always been the case. Amazon was originally a book seller.