They used to say not to stand a baby on their feet because it was developmentally inappropriate and caused bow legs. I believe it's called exercise.
I also believe in exploring things and situations with baby. Bumbo had entertainment value for HER. She did not use it much, and certainly didn't live in it.
Perhaps leave newborns laying on their back so that you don't force them into positions they cannot get into themselves? *scratches head* Hmm...
If you want to call me dumb, go ahead. *shrug*
My daughter is not delayed, maimed, weak, or otherwise altered from having spent a few minutes laughing her head off sitting in a goofy little chair.
No, she did not need Bumbo. Who cares? She thought it was a riot. We like to offer her diverse experiences.
I don't know what damage you're claiming it'll do, but this baby is not suffering.