In Spanish it is very common for the "d" and "r" sounds to be very close to each other, and there is a huge range of ways in which people pronounce "d" and "r" between different regions and dialects and even individuals.
The way certain people pronounce "r" may sound very close to how other people pronounce "d". Usually, with a given speaker, you can very clearly hear what they're saying if you know how they speak, for example, some people/regions/dialects pronounce "d"'s more like a "th", and other people don't even pronounce the "d"'s at all, especially if they are surrounded by vowels and close to the end of a word (this is super common in Puerto Rico).
So basically...yeah...I get that it sounds that way...but...if you want to understand a range of native speakers you're going need to to get used to this. I personally am grateful for how DuoLingo varies these things up...it keeps me on my toes and I think helps me more than it would if they stuck exclusively with a very standard, clear, or "middle of the road" pronunciation. So it's like, yeah it's frustrating and makes learning harder...but...in this case it might be good that it's frustrating.
The pronunciation and indeed the word choice Duo uses reflect a Latin American Spanish. We don't hear the c/z lisp. We don't learn the vosotros form. We don't learn Castillian-specific vocabulary. While the Spanish 'd' is softer than in English, this pronunciation isn't right.
I like to study on my phone because I can use Dragon's dictate app so I can dictate rather than having to type or swipe. Just for kicks I decided to turn on Dragon and play the recording to see if Dragon could understand it. After many tries it was unable. However it understands my pronunciation just fine.