The word ladder problems have an aim: to find the shortest solution. There are probably thousands of answers for each word ladder, but most of them won't even be thought of because they don't give a short solution.
For instance
DARK -> LARD
You would probably think of DARK - LARK - LARD, and you wouldn't think of DARK - PARK - PERK - BERK - BARK - LARK - LARD. This is because you want the shortest path and there is obviously a shorter solution.
This aim makes the puzzle on-topic. There are tons of solutions, but they are obviously better ones. One answer will be better than another.
However for your puzzle, all answers will be exactly the same, no answer will be better.
This makes all those thousands of solution valid, and this is too broad.
You need some parameter or aim to make it not too broad, for instance:
Find a grid that uses the least amount of different letters, with all different words.
This provides an aim, and a solution with 26 different letters isn't going to be as good as one which uses 5.