It works as it always has. You simply have the wrong computer for AE work and you will suffer these slowdowns with many other functions as well. AE is barely multithreadced, does not have fancy parallel processing and also almost no GPU usage except for basic drawing functions and some effects. For more detailed answers and explanations refer to the gigazillion "How to optimize performce?" threads where I and others have explained things over and over again. Still, doesn't help you. It's still the wrong, not so ideal computer.
8K footage is going to take a very long time to analyze. There is no real way around that. The best you can do if you want to use the original footage is to trim the footage so that only the frames that absolutely need to be camera tracked are included in the clip.
Another option is to drop your 8K footage into a comp that has been sized down to about 1920 pixels wide using the same frame ratio, scale the footage to fit horizontally, then pre-compose the scaled footage layer and Camera Track the smaller comp. When the track is done, you have set up the origin and ground plane, and you have attached reference solids to the surfaces you need to track, use the Demo Panel from the File/Scripts to open up the Scale Composition script and return the comp to the original size. You can then delete the pre-composed footage and replace the pre-comp with the original footage.
One more thing. Please use the toolbar to embed your screenshots. Uploading them makes them a real pain to look at.