You can mine on any computer.
Not if you actually expect to get anything. I mean, technically, I could get some bitcoin if I mine 50 years on my home computer, but that's not reasonable to expect of people.
You have to get specific machinery that has high processing power - and you MUST get that from a third party.
To get a paper wallet, I have to go to a third party website. To get an encrypted wallet, I have to go to a third party to buy it. To get an online wallet, I have to go to a third party to buy it.
To do transfers, I have to go online (third party) to buy it.
I see a pattern. Why can't you?
Don't deny the importance of infrastructure in crypto. It is not a decoration. It is ESSENTIAL to making crypto a long term player in the financial/investment space.