Back in the 90s, it would have been nice for BBC to have tried to dramatise the other three books, but they'd have needed a lot of puppetry, or for technology to advance rapidly, to avoid more human actors playing the animals. 

Keeping them human would have kept the series consistent, if a bit old fashioned. On the British stage, generations of children have seen humans play animals (both humorous and serious). The theatre group I work with only started using puppets in the last 15 years, and required children to use their imagination before that.

Lewis's animals are a step forward from his childhood stories, however. In Boxen the creatures were basically playing adult humans, whereas in Narnia they all behave like the creatures they are, despite talking and thinking.

I'm not sure I miss any of the proposed adaptations. Most of them would have been disappointing. They seemed to be aiming at a modern teenage audience that enjoys American action movies with no Christian faith elements. The two original Walden scriptwriters were once quoted as saying that 'Susie' was the voice of the author.  They had clearly never understood what the books were, or what they were saying.