Old English was a Germanic language. Grammar-wise was a lot like modern German or Dutch. However, as English evolved, its grammar was greatly simplified, and nowadays only a few vestigial features of the original declension system remain.

But the declension system is not the whole grammar.

So while articles don't change much under declension, words like "a" and "the" are familiar to Germans but not to ancient Romans (I don't know about the French). Also the relative order of adjectives and nouns is Germanic. Conjugations, while simplified, still retain much of the old structure, and the set of tenses understood in English is quite Germanic.