Yes I can totally hear the difference. Ridden - you pronounce the d as a d. The r is a hard sound. Written - you pronounce the t as a t. The w is a whisper sound. You can hardly hear it. I don't know how to explain this. Can any other native speakers help?

You certainly can in the British / Commonwealth accents. Not too sure about American.

It's difficult to say whether we hear the difference or not. That will depend on the accent of the speaker. In standard British English, the initial sounds (wr and r) are the same but the d and t sounds are not the same. When said quickly they could sound similar. In other accents, they may be pronounced the same way. It depends. In practice, they'd never be misheard because there wouldn't be a context in which either word is possible. They would have totally different objects - there are no things which people both write and ride.

I can see why you have asked about this - in normal casual speech they do sound the same. Few people will pronounce the d or the t - these are typically reduced to a glottal stop, and even this is masked by the ‘n’ at the end, so what you hear is ‘ri - n’ where the ‘n’ is formed by putting the tongue between your teeth and vocalising while breathing out. Some styles of English may provide better enunciation, and the South African accent spoken by Brends could well distinguish better between them. I personally like that accent and it is a good one for English learners to listen to for clarity. However this won’t help in other situations and you should rely on context ; it’s unlikely that these words could be misinterpreted in normal use.