It wasn't impossible. There were basically two solution up until now: use an alternative browser with ad blocking included (e.g. iCab), or a VPN that filters ads for you.
This isn’t sufficient, you’d still get empty squares everywhere on the pages with ads.
Really depends, it's worked quite well for me on most sites. Granted, I use it with an iPad where this is probably less of an issue than on the much smaller iPhones.