Can you explain/point out the lacunae? It’s an index, much like a stock index. It chooses certain parameters, scores countries on those parameters, then applies some formula to convert those scores into a single number…exactly like a stock index.

It’s self evident that their parameters can’t cover every nuance of every country.

But, under the available parameters, if two countries have the same score, it should be safe to say that the countries will be roughly the same in that parameter.