You said "a similar range of services". Basic DDoS protection is probably important, and there are other companies doing that. Beyond that, it's less obvious.
They are advantageous to leverage in certain situations but essential they are not. We're used to, in the technology industry, looking for or creating problems to solve with services we are aware of. Moving back to necessity and need, do we really? Are we being objective? Most of the time, no.
Theres a few alternatives, but at a minimum yes you probably need their or a competitor's Name Servers and their public DNS. Rolling your own isn't very feasible.
DNS hosting is easy if you did want to roll your own, but everyone one does it, especially your registrar. The more sticky bits of Cloudflare are their cloud services, specifically compute (workers) and database and object storage, all wrapped up into a convenient product (Pages). Also their identity and VPN stuff. They've come a long way since just doing DDoS protection/being a CDN.