Yes, to *completely* remove the text and show what was "underneath" is really, really, really hard. You have to re-construct what was hidden. It can be done with still shots, but for moving footage? Forgetaboutit!

Your best bet is to either crop out (zoom in) the text .. or .. cover it up with something else you added.

If the video is a static tripod shot it's pretty easy.

For a panning shot, it's very difficult, and depends on the scene.

For static shots you take a screenshot and clean the jpg in Photoshop using the clone tool or whatever works best and crop to the smallest size possible and feather the edges to no background. Then use this as a mask.

For panning shots, another way to approach it is to place two copies of the video on the timeline and pan and crop one to a small area adjacent (above or below) the text to be covered that is similar and the same size as the area to be covered and overlay that. In some cases that will work.