You can stand the additional height of the new tile over the old, you can just put the new ceramic tile down over the old.
Be sure to strip the floor of any wax, grease, soap scum, etc. Then scuff the floor with a 40 grit sandpaper. Then use a high quality thinset motar such as TEC. You should have no problem.
If the old floor is spongy and deteriorated, then busting out the old and building up with two layers of cement board (be sure the seams don’t line up)would be a good approach.
Good Luck!