Cannot access blocked websites even after using Cloudflare dns

Basically title.

I am trying to access a few website blocked in my country but can’t even when I changed my dns to Cloudflare’s on my router.

However when I tried using their app on my iPhone it installed a vpn configuration and I was able to access said websites. Why is changing the dns on my router not working?

(Dns caching on my phone shouldn’t be an issue as I checked my dns on a website through it and it says it’s correct).