It is often faster and cheaper (particularly if you are paying for labor, so faster is cheaper, but merely saving your own time is good, too) to either cover the wallpapered wall with thin sheetrock, or bash out the wallpapered wall, do anything a sensible person would do with the wall open, and place new sheetrock.
This seems like a drastic, nuclear option approach when you are thinking "but I just wanted to remove the wallpaper!"
You can waste a lot of time and effort and products trying to get an old wallpapered wall looking as good for paint as a newly sheetrocked wall. Demo is messy (so is wallpaper removal) but quick. New rock is quick...and you can fix any wiring or insulation issues in the wall. There's another wallpaper removal question where where one answer says they spent 6 nights doing a 10x10 room sure, it was the worst room, but tearing out and new rock would definitely have been faster, in my experience.