So they worked a lot to get to the position here and no one else wants to make the same efforts. There's no easy play here
Plenty of people do want to make the efforts and have tried. Physical retailers like Walmart have opened online retail but adoption remains limited. Startups like Jet.com, Quidsi, Fab.com, Rakuten/Buy.com, Woot and many others have tried and failed to take on Amazon, leading to bankruptcy or being sold. The reality is that nobody can take on Amazon due to their slimy tactics but also nobody can realistically provide something to customers that Amazon doesn't already provide. Fees will keep increasing and costs inflating as much as Amazon wants, while customers are none the wiser and sellers can do nothing about it.
What you say is contradictory.
If fees and prices are increasing on Amazon it means more potential for the competition if they can operate with lower margins.
Amazon is winning because they toe the line, not because of an innate monopoly.
If you read the parent comments we've already established that Amazon punishes sellers for pricing lower on other platforms than Amazon, and Amazon's margins affect item pricing everywhere. You could have zero margins, you could have negative margins, Amazon will see that Seller X's items are available on your Amazon competitor for $2 while it's $20 on Amazon and say that they're in violation of policy. Unless you make it worthwhile for Seller X to abandon Amazon you will not be able to compete.
You won't be able to just replicate their strategy, and they've spent ridiculous amounts of money on next-day/same-day delivery infrastructure that nobody's gonna be able to invest that much. But if you do have any ideas on how to disrupt Amazon and be more convenient than them in 2025 let me know :)