Some sites not blocked, /etc/hosts
The hosts that are not being blocked successfully are probably already in your DNS cache.
Try clearing the cache using:
sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder
if you are on Big Sur (looks like you are), or:
sudo killall -HUP mDNSResponder
if you are running Catalina, Mojave, High Sierra, or Sierra.
You may also need to clear the browser cache. For Safari, go to Safari -> Preferences -> Advanced and turn on "Show Develop menu in menu bar". Next, in the Develop menu, chose "Empty Caches"