I watched this thing as a kid and thought it would be a pretty good movie if they weren't singing all the time and for no reason. Were the songs supposed to be dialog? But every time something starts to happen the movie stops dead and they start singing.
There was a time when musicals were thought to be somehow educational. So I got dragged to see Oliver! and I've had a grossly distorted picture of the work of Charles Dickens ever since.
Mark Lester, a big child star in his day who played Oliver, was reportedly tone deaf and arhythmic. Just plain couldn't sing at all. His singing was dubbed by a five-year-old girl.