They had a personal block list at one point... but removed it.

There are browser add-ons that can do this (for example, uBlacklist).

Kagi has that feature.

Why not just create your own search box and put -site:domain.xyz in the query? Maybe there is a length limit but at least you can ban some

There is a chrome addon called uBlacklist that auto-hides domains (configurable) in the google search results.

this list is really helpful

https://github.com/quenhus/uBlock-Origin-dev-filter