She’s significant to the current throne because she ties the present dynasty to the Stuarts and later Plantagenets. (everyone after Edward III). Doing Elizabeth’s genealogy, she is *very* significant. I’m not sure if that is the same for Charles or William.
I looked that up and was surprised to find the entire lineage actually goes back to the first traces of the formation of the Monarchy, to William I (The Conqueror) and even to some of the warring pretenders to the throne beforehand...pretty fascinating and surprising - I thought that throughout history the throne had probably been taken by different powers at war coming in and taking over...but all of the squabbles over the throne were actually inter-family when they took place...not always immediate family, but still family. Just a brief interruption by Cromwell to their continuous reign.