I'm not very knowledgeable about clutches, but I have driven a high and low mileage mustang of the exact same year and model and my clutch was firmer than either of them.
('00 v6 5spd, quite firm, slow to engage)
others i've driven:
('01 v6 5 spd, slow to engage, VERY easy to push down)
('00 v6 5spd, slow to engage, easy to push down)
Unless you notice some issues with it, it most likely is just how it's going to be (nothing is probably wrong with it)