If 1Blocker extensions appear greyed out in Settings > Safari > Extensions, it seems that you have some restrictions enabled on your iPhone.
No worries, you can manage them easily, and here's how to do it:
Go to Settings > Screen Time > Content & Privacy Restrictions (enter your passcode if required).
Scroll down to the Content Restrictions section.
In Content Restrictions, go to Web Content. You'll need to set it to Unrestricted Access in order to activate 1Blocker. Alternatively, you can just turn Content & Privacy Restrictions off.
You should now be able to turn on 1Blocker extensions in Settings > Safari > Content Blockers.