You could say the same thing about Russian. Like German, it doesn't borrow very heavily from other languages; and a lot of the words are simple variations of each other with different prefixes and suffixes. It was even the Lingua Franca (or "Latin") of the Communist bloc.
On the other hand, Russian might be an even harder language to learn than German, given that it's Slavic and uses a different alphabet. There's always Esperanto, which has more than 200,000 articles on Wikipedia; more than Latin even.
Russian doesn't borrow heavily? There's a ton of borrowing from French in Russian.... I hadn't appreciated quite how much until I started learning French.
Lots of borrowings from Turkic languages as well. For example the common word for money "dengi" has the same roots as "denge" (balance) in Turkish and national currency of Kazakhstan "tenge".
On the other hand, Russian might be an even harder language to learn than German, given that it's Slavic and uses a different alphabet. There's always Esperanto, which has more than 200,000 articles on Wikipedia; more than Latin even.