You can get a good app from an original developer using an appstore. The problem you described is not that genuine developers cannot share their apps, it's that users are taken in by fake apps pretending to be genuine.

If it was the norm to download a signed binary from a random website, random websites looking genuine and offering genuine fake signed binaries would be the norm. "Are you sure you want to install Adobee PhotoShop? (Signature verified!)"

"No mom, Adobe PhotoShop!"

"I have Abobe PhotoShop, Adode PhotoShop, Ádobe PhotoShop, PhotoStop by Adobe"

"Mommmmm"