Sure, having no unification at all would be bad, but the issue is with the gray zone. Some characters are written identically in each CJK language, but among those that aren't the amount of difference varies widely. The trouble is that Unicode leaves separate codepoints for each version that somebody, somewhere decided were "different enough" (even when they are the same character historically and linguistically) but merges many characters with (consistent, well-defined) differences because somebody felt they were close enough for horseshoes. People often think that characters were only merged if they were linguistically the same, but that's not the case.

Also, comparisons like "different ABCs for English and Spanish" are spurious and unhelpful. If you could tell an English "b" from a Spanish one by looking at it, the comparison would be sound.