How is that any different than any other domain registrar though? There's nothing stopping you from just moving the domain to another provider if it's a problem.
Compared to the Namecheap and GoDaddy stories, Cloudflare has been a gift to use.
I feel like you haven’t read how domain transfers work and are regulated. Cloudflare deciding to bill you for something else doesn’t affect your domain ownership or rights in any way. Should they ever make such a decision then you just transfer them to someone else.