It is, though. Safari has native support for 3rd party adblockers, it’s just that many people don’t know. AdGuard is one of the good options. Safari is doing the actual blocking for the most part (the extension just hands over the filterlists), but nowadays some of the adblockers include an optional extension that applies some rules for complex ads that are not supported by the Apple API, such as on YouTube. As an end user you just have to install and enable the adblocker.
Then there are also other browsers available with built-in adblockers. Admittedly those are all limited in some ways because they’re forced to use the same browser engine (outside of the EU), but they are very effective at blocking ads.
But 2K and 4K do refer to the horizontal resolution. There’s more than one resolution that’s referred to as 2K, for example 2048 x 1080 DCI 2K, but also 1920 x 1080 full HD, since it’s also almost 2000 pixels wide. The total number of pixels is in the millions, not thousands.
For 4K some common resolutions are 4096 x 2160 DCI 4K and 3840 x 2160 UHD, which both have a horizontal resolution of about 4000 pixels.