I agree with the OP. My sight is fine, not as good as it was twenty years ago, but when I face thirty lines of solid text that is not divided up at all, I leave that post and go on to a different one.
It is nothing to do with grammar or perfect English, it is just the sheer bulk of it - like eating a suet pudding continuously in one mouthful, having the next forkful shoved into my mouth before I have swallowed the first. The absence of any full stops or commas has the same effect on the brain, and reading something with neither punctuation or paragraphs leaves me as breathless as if I had run up three flights of stairs without taking breath.
The paragraphs don't even need to be cut up into bits with the meaning separate in each chunk - it could be chopped up randomly. Just go down the finished post before pressing send, and press enter or do a line break after every two or three sentences.
If you don't believe me, open a couple of printed novels in a bookshop and compare long pages with no breaks with ones where there are three, four or five paragraphs to a page. Which would you read on and on, and which would you put down pretty soon and go and make a cuppa? would you rather people read your post or abandoned it or read to the end, understood it and answered? If you find your posts don't get an answer, could this be the reason?