Hey @pretvari! 
It looks like you have set A records on the www subdomain. You will need to remove the two A records on the www subdomain, and replace that with one CNAME record as mentioned in your Project Settings.
www → proxy-ssl.webflow.com
The reason why the root domain cannot be currently set as a default when using A records is that those A records would need to be dynamic as the IPs change for how Webflow resolves on Amazon Cloudfront across the global network, with the way this works as a CDN. The proxy CNAME records allow for resolving to dynamic IPs.
Because the IPs are not static, if static A records were set on the root domain to have the root domain load as default, it would not be optimal for everywhere, and the IPs subject to change so the website could stop working if IP routing changes.
If you want to set the root as default, you would need to use a service known as CNAME Flattening. It is explained more in this article here: Set root domain as default domain | Webflow University
Hope that all helps!
Cheers