Earlier quoted context omitted.
NextDNS lets me pick what to block, I can't configure DNS0 except for the few variants that require me to change the DNS address completely. Also: I can't pay for DNS0, so how can I trust they stay up when I'm not their customer?
How can you trust any company you pay to stay up even if you are their customer? I've used discontinued products before. Paid subscriptions to companies that merge with others and the service no longer really exists.
It's like Google's stuff. It's free, but you're not the customer, you're the product.