First of all, that's the terms of service that you agree to when signing up for an account. If you don't sign up for an account, you haven't agreed to that.
Additionally, you left out this from your quote "(except as provided in Section 2.3 of these Terms of Service)". Section 2.3 says "You may download or copy the Content and other downloadable items displayed on the Services for personal use only, provided that you maintain all copyright and other notices contained therein". All an adblocker does is download some of the content and decline to download some of the downloadable items. That's permissible under Section 2.3.
Additionally, you left out this from your quote "(except as provided in Section 2.3 of these Terms of Service)". Section 2.3 says "You may download or copy the Content and other downloadable items displayed on the Services for personal use only, provided that you maintain all copyright and other notices contained therein". All an adblocker does is download some of the content and decline to download some of the downloadable items. That's permissible under Section 2.3.