Oh, if you were expecting something like the images produced by the original DALL-E, then I totally agree with you, DALL-E Mini doesn't get even close to that level.
My guess is that it is be due to the combination of it being a "DALL-E Lite" model overall and (most significantly) only running for ~150 iterations max (using the website linked in the OP). ~150 iterations is way too few iterations to get something approaching the type of images you've seen from the original DALL-E
