I’m not sure if this already exists, if so I couldn’t find it.
I think a feature that let’s you block specific sites (e.g. YouTube, facebook) would be a great addition to the mobile version for users like myself that might want to prevent themselves from wasting time on specific websites, as apps can be uninstalled but everyone uses a browser often people start using the same distraction there.
I think this feature would be useful to many people seeing every desktop browser seems to offer multiple successful plug-ins that do this.