The thing with famous voice actors (or famous actors in general) is that they can cause counterproductive mental associations, unless they have
impressive voice range or acting range.
For example, I know that Patrick Stewart has done some voice acting for animated works in the past (including an English dub of Nausicaa, IIRC, so that makes him a particularly on-topic example here). Whenever I hear Patrick Stewart's voice for an animated character, I
instantly think "Captain Picard". And not long after, all of the feelings and impressions and sentiments I have for the character Captain Picard ends up getting spilled over unto the character with Patrick Stewart's voice. This isn't so bad if the character being voiced by Stewart does in fact share some similarities with Picard (which partly explains why I was fine with Stewart as Charles Xavier and felt he was great for the role). But if Stewart is playing a very different character (such as a villain, for example), then that can cause painful cognitive dissonance.
So famous voice actors and seiyus can cut both ways. They can make a character more popular but they can also consume a character through counterproductive mental associations.