Five percent seems like quite a lot, given that most payment processors charge less than three percent. What sort of value do they add outside of payment processing?
Depending on how much time you have, some of those features can save you a bit. Not sure how that compares to other widgets like itch.io though.
Even scrolling through my GOG collection of games I'm somehow too lazy to play instills in me a sense of pride that at least they weren't purchased on Steam.
Though there are also major practical advantages of purchasing things within stores like GOG and Steam instead of a bunch of disparate websites: when you move to a new computer, you don't have to chase down a bunch of websites and license keys and emails to reinstall all of your software. Which is something I hate so much I only got outside of platform shops as a last resort.
If the product payments are typically below $10 then it makes sense to use Humble.
Trying to figure out which county in some state you owe $0.14 to is a nightmare.