I've heard it for many times, and as a native Russian speaker I can't really judge because obviously my language sounds normal for me. I tried to analyze, and I've found that I just can't understand what people mean by saying "harsh". So, there's a video with normal speech in Russian and a song, and I'd like you to listen to it and write which sounds or words or something sound harsh or unpleasant to a foreign ear.
Most of my collegues use swear swords and that is why their speech seems crude and roughly and harsh. That is really boring. Literate russian speech is beautiful and pleasant.
I spent some time learning Russian. If I want I can make it sound harsh, but I can also make it sound soft and nice.
I think the main reason for it sounding harsh is the way so many consonants are grouped together. It is a very consonant heavy language without a soft "o".
Кто for example. There are few languages with such a sound pair of the K and T.
The Russian speech Siberia sounds not so melodious , sounds like - o- definitely are more short .
And there are regions with very specific intonation , being in Tumen fist time , i just wanted to lough hearing how the citizens speak , i guess it is so not just there , i mean specific intonations
