Replacing treads is hardly respectful of the fabric of the home and undoubtedly not cost effective.

Why not refinish the stairs?

It's going to take a lot of sanding to get thru the stain and down to bear wood. Even if you do and then restain them I doubt you would get an exact match. Replacing the treads might be easier and even more cost effective than trying to refinish them.

I think whether or not the stair treads would be easy to replace is going to depend a lot on the construction of the stairs. My treads could not be replaced without removing the stringers because of how it's all attached together. If there are spindles set through the treads they may also not be easily "just replaced".

Show pictures. While it might be possible to strip and stain the dark stained stairs, the labor cost to do so (unless DIY) is likely more than replacing them. "Capping" should not be an option. Your stairs must meet the rise and run codes.

Yes even though the capping material is thin, your feet are "programmed" neurologically by two steps, for the remaining steps, and if the first or last one is relatively higher or lower than the rest it can create a tripping problem (too high) or a too tall last step on the way down which can give you a jolt even though it is a relatively small difference. There is a video I've seen of people walking out of a subway and there is something wrong with one of the steps --it's temporarily slightly off, and it shows dozens of people tripping in that spot on the way up.

Have you thought about painting the treads black and adding a runner . I really need to see the stairs and the new flooring .I do agree stairs have to be perfect .It is best to try to see how hard the existing finish is to remove . Please post pics of the stairs here in a comment so we can get a better idea of the work .

I have thought of paiting them, but the shape is dated I think as are the spindles.

What do you mean the "shape" is dated? Stair nosings are required by code.

@DeWayne I may not be using the correct terminology but the piece on the floor is very round and we’d like more straight edges.