You're right about their being relative unknowns back then. In fact, the oldest one to use celebrities was Alice in Wonderland Ed Wynn, Jerry Colona.

But here is a good question would a lot of kids know who the voices are for the film that came out whether they are major movie stars voices or unknown voices no matter if it is Robin Williams, Eddie Murphy, Mike Myers, Ray Romano etc.

I don't like it. I don't mind one in a movie, but generally couldn't care less.
All this proves is the not-so-Disney co. is banking on star-power, and maybe doesn't have much faith in the actual story and presentation.
And compared to the real Disney collection, yeah, they fall short big time. Some are good, some OK, but compared to Walt, they collectively are 2nd-rate.

And plust for Shrek Mike Myers used a Scottish accent for the lines that he recorded his lines for the movie. I don't know would you count Gilbert Godfried as a famous face as well? It shows you who different animated movies today are, when most of them have major movie stars in voce roles, when a couple of decades ago not as famous. The most famous name in Beauty and the Beast has to be Angela Lansbury. And even when you go back to Walt Disney's day he used professional voice artists rather then any of the major celebrities of the day.

I don't mind celebrities being used at all, especially when they contribute something unique like Williams did, but when the cast are
all
celebrities it can get a bit overwhelming.

I don't like it either. Usually those celebrity voice actors aren't as good and have pretty annoying or plain voices.