Direct-to-consumer businesses have taken off due to the internet. It’s never been easier to start a sock company or glasses company etc. Historically you had to get in to the big box retailers to sell anything non-local but the internet has flipped that on its head. Even big platforms like eBay and Shopify (and even Amazon) are offering small businesses and individuals way more opportunities to sell than they would have had pre-internet.
Furthermore in a direct to consumer world, incumbency matters way less. People had fewer options pre-internet (whatever was at their local store) and now brands largely compete on quality (reviews/ratings) rather than pure placement and marketing.
And yet all your local retailers are closing down while Amazon gets bigger every year.
It applies basically everywhere. while you're correct that its easy to get started on Amazon, it's just as easy to get marginalized there. There a tons of reports from sellers which got ruined by Amazon undercutting them after they've pioneered the market for example.
The internet enables centralization like never before as everyone all over the world uses the same services just like they're following the same people for entertainment.
The newer people who joined the internet late are on a handful of sites they see as safe. They came from the mobile phone era and they include grandma and your ex-school teacher. The people who were here before joined them because that's where the action was happening.
Google decided to go with the masses and dumb down the results to only a handful.
Offtopic: The only day I tried a specific search with quotes in duckduckgo and google. Only duckduckgo had it. Makes me wonder what I've been missing using google.
More consumers begets more producers. I would assert you have better odds of producing in a wide variety of areas.