I kind of wonder why ISPs haven't already started offering value-add security services that have various levels of filtering to provide a cleaner-feed internet experience.

From my limited research there seem to be a surprisingly large number of bad actors that own moderate swathes of ip address ranges and even Autonomous Systems (AS) that are known and can therefore be blocked.

I use OPNSense, which seems to allow AS blocking in the firewall rules, and also have some automated blocking based on external malicious IP address lists. My not very well maintained project can be found here: https://github.com/UninvitedActivity/UninvitedActivity

I have no idea if these sites would have been blocked by my setup.

Another concept I like but haven't put the research time into is blocking recently registered domains (RRDs). It would appear to be the case that RRDs probably aren't crucial to the average persons daily browsing experience, so blocking them for a certain period of time shouldn't cause too much hassle. There are some services that list them - problem is that there can be tens of thousands per day, which can be difficult to manage into lists compatible with various blocking softwares ( I haven't found how to automate it for pihole yet - but I haven't tried very hard either).