It's still useful for comparing potential performance of algorithms with different O(x). e.g. an O(n) algorithm will most likely outperform an O(n^2) algorithm

It's still useful for comparing potential performance of algorithms with different O(x). e.g. an O(n) algorithm will most likely outperform an O(n^2) algorithm, but two different O(n) algorithms can still perform quite differently. But you're right, it's meant for comparing scaling.