Bash Alias Not Found Error
Instead of an alias use a function. Also,I wouldn't use find's placeholder- {} as a parameter in the inline script.

csfiles () {
find . -maxdepth 1 -mindepth 1 -type d -exec sh -c 'for dir
do
        echo "$(find "$dir" -type f | wc -l)" "$dir"
done' sh {} + | sort -nr
}