Developers generally require a credit card for collecting itch.io payments.

Can itch.io just extend this to debit cards too? Or maybe give us the option for PayPal accounts.

Forgive me if debit cards aren't used for collecting payments. I don't know much about that.

Debit cards and credit cards only differ in whether your bank allows you to overdraw. From a technical standpoint they're the exact same thing, and neither itch.io nor PayPal make any difference. :)

Although I don't have  a credit card (I acquire a debit card only; my dad's card :P) and itch.io has the ONLY option to collect payments i.e. credit cards.

I'm under 18 years old, the bank won't allow me to get a debit or credit card until I turn 18.