Those did suck, until erasable pens came around and they changed what the blue stuff was made of, if memory serves. I remember those early erasable pens that had a similar blue eraser in the cap.. usually only worked if you wrote lightly, but the ink tended to be kinda thick and required force to write.. so you’d always have that blue smudge left over and could probably read what was written anyway.
On a related side note, has anyone tried the frixion line of erasable pens? I got them for my knockoff rocketbook (a planner-size notebook of “paper” made from stone fiber, in which you can erase special pens like frixion using water, like wet erase markers, or the eraser, and reuse the paper indefinitely) and even on regular paper they are just amazing to erase. Every color comes off cleanly, and the eraser is just a rubber nub of some sort that doesn’t wear out.