Because it is already sealed you can't just apply stain- nothing to sink into.
Stripping to bare wood is tons of work. It could be "toned", putting color or stain into the clear finish and layering up to desired look.
Easy to have it look sloppy unless you are good with the materials and brushing technique.
"It's better to come here with questions before you screw up than to come here after and ask how to fix them."- JS
Agreed. You would have to strip whatever protective finish is on there off, then try to pull out what stain you can. Sometimes coating the stripped surface with something sticky like shellac will work. Then use stripper to pull all of it out of your way. Some will be left in the grain though so when you pick your new stain color, practice on an inconspicuous section. Once you have the new stain color you like. Apply the stain and a couple coats of protective finish over it.
It is lots of work but worth it if you really hate the color.
As BJ suggests there are other ways to do what you want in a less pure and authentic way. I don't like using them but have. Gel stains are designed to go over prefinished but scruffed up wood like in the situation you have. There are different glazes you can buy too. If you have one near, a real woodworkers supply will have the best options. Your real paint store would be a good second choice. Under no circumstances should you trust a gel stain product from a box store!
Just curious. What is so offensive about the wood color you have? I realize I ask for esthetic comment here. I have worked on places where the oak in a light color made no sense at all. Others where it seemed somebody tried to disguise it as charcoal burned walnut or something. It looked so out of place. You cannot and should not hide the true grain of real wood. I suspect you inherited what you have though?