Honestly I really like CloudFlare as a business. There's no vendor lock-in, just a genuine good product.
If they turn around later and do something evil, literally all I need to do is change the nameserver to a competitor and the users of my website won't even notice.
Then you're not using any of their services besides DNS, at which point you don't need to use Cloudflare at all.
As soon as you turn on any other service they offer, you need to actively migrate away. It's an inherent issue of services that actually provide a benefit. If you're saying "I can just migrate to any other nameserver" then you're telling me you have no use for Cloudflare in the first place. Because if you did, you couldn't just not use it anymore.
Let's say you're using their WAF. Sure, you can just change your domain's nameserver and you've migrated away. But now you no longer have a WAF. Same for their CDN. Or their load balancer. Or their object storage. Or their CAPTCHAs.