Why DNS changers block access to the internet?

[GranPaSmurf]

I've tried DNS Changer and Cloudflair 1.1.1.1 — both prevent me from connecting to the internet.
Do I have something configured wrong?
Galaxy S7 Edge, Oreo

 

[Rukbat]

You put your website on Cloudflair? Or you put your phone on Cloudflair? Cloudfare is for websites, not phones.

If you want to change DNS servers, try

Google at 8.8.8.8 and 8.8.4.4
or
OpenDNS at 208.67.222.222 and 208.67.220.220