I believe it's safe to say that the IE language was borrowed by non-native speakers, that's the only possible way to end up with 20% non-IE vocabulary.

But, except for that, the Germanic languages are IE. Consider; the Germanic languages case(d) their nouns. It may not be as noticeable anymore as Latin or Sanskrit, but that just means they've simplified over time, like all the other IE languages.

Germanics inflect their verbs. I'm not too familiar with the other IE languages, but I think their auxiliary verbs are unique to the Germanics. But that's where it ends. It conjugates for infinitive, 1st, 2nd, & 3rd person singular & plural, just like all the other IE languages.

Then there's the mannor in which they do these. AFAIK, the Finno-Ugrics perform these functions by adding suffixes. I suppose that's kind of what the Germanics are doing, too, but they do it by replacing endings, rather than adding endings.