Age change in Théoden

[Sauron the White]

from A Little Green

Anyway, the question I think was not on whether Bernard Hill succeeded as Théoden but rather why wasn't he made older. Simple as that.

And why should he be made to be older when Hill as Theoden was already depicted as old?

The implication does not even have to be surmised as the answer is directly in the first post by MatthewM to begin this thread

Why do you suppose Jackson made King Théoden (and in turn his son Théodred) appear about 20-30 years younger than Tolkien described him in the book?

It right there clear as crystal. The poster is comparing the Theoden of the book to the Theoden of the movie. That is his standard and that is the basis upon which he frames his question.

One cannot judge the qualities and success of one medium by applying standards
and qualities of quite another. That is fundamentally flawed and unfair. It serves no end or purpose but one: to continue a debate which you yourself characterize as pointless and ridiculous.

In point of fact, the real question is indeed whether Theoden as portrayed in the film worked in the context of the medium of film.