Sure, it would be equally difficult to start a new company making non-niche[1] t-shirts or toilet paper or plastic cups or light bulbs today.

1 - "non-niche" a/k/a the undifferentiated "standard-quality" product in the middle of the niche. This is not about someone inventing a longer-lasting light bulb or stain-resistant t-shirt. The best analogue to farmers selling commodity soybeans is something closer to plastic food wrap or aluminum foil. Not a lot of small operators playing in or entering those spaces either.