[aniviacat]

> developing isn't for developments sake.

[citation needed]

> the person who makes that product reaps all the monetary benefits from the work that the others have made

Which means that they can offer their product for a lower price, which then benefits the general public.

Companies being able to operate cheaper / more efficiently does benefit the general public, as long as the market isn't a monopoly. And as per my above comment, most markets are not monopolies.

> open source developers never make a product polished and user-friendly enough to be usable by the general public

I've been using Audacity, Gimp, Inkscape, uBlock Origin, and many others long before I knew what FOSS means. Spliit is also pretty cool ;)