I don't know if you're considering what Coinbase is when in alignment with cryptocurrency. It is exactly what cryptocurrency was supposed to not be. It's centralization, it's a bank. I personally have no emotion towards it, but I definitely understand those who do as the cryptocurrency project was quickly taken over by the same old financial interests.
False. The objective of crypto isn't to force everyone out of the banking system, it's to provide an ability to opt-out and be your own bank for those who need or want it. If you want to use a traditional bank or custodian instead, go for it. And indeed, for many people who cannot and should not be managing their own keys, it's the preferable option.
You need fiat on ramps for crypto to work. Contrary to what other commenters have suggested you can't legally help other individuals convert their dollars to BTC. That's acting as a money transmitter.