Same here. Do you have extensions on, specially ad blockers? I have, and I get the filling that it. One thing that worked for me was disabling ad blocker extensions and use this https://hblock.molinero.dev/m installed through homebrew. Safari got much faster.
Hosts url: https://hblock.molinero.dev/hosts
Carefull, it's a big hosts file, not recommended for less powerful devices, and don't try to add more hosts sources, it likely already included here.
No, i use AdAway to fetch it from that github link (along with other sources like hBlock)
Said github link is not my work, but by some guy called 'Anudeep'.
AdAway is for Android, there's PC equivalent called "HostsMan".