I think it is a basic question if you will not understand what is written or what the blogger is willing to tell their audience then it will be no use, or it doesn’t have readability,
Then forget about the SEO score, it will not able to get the normal attention of your readers with a high bounce rate and it will be a complete waste.
How it related to SEO-score, you can understand it by below given two points,
1.Search engines copy human intentions
2.It helps in voice search and accessibility &SEO -score
The first one!
1.Search engines copy human intentions:-
It is true that Google is now giving more value to human intentions than keywords,
The blog filled with target keywords is not giving good results in SEO-score nowadays google started recognizing synonyms and which words, entities, and content are related to each other.
So if your blog is good in readability then it will match with search intention as it will make a sense.
The second one!
2.It helps in voice search and accessibility & SEO-score:-
How does readability help in the Voice search and accessibility,
Consider a situation where a blog is filled with difficult words and not arranged in a proper way than for voice search someone read it aloud,
It will be very difficult for Google to understand it as it will not make any sense so it will not fit either in voice search or in a normal search, as result, it will affect SEO-score.
Consider another situation when visual impairment might use a screen reader to go through your content in that case it will be very difficult for them as it will be difficult to understand.
Readability provides a blog complete sense and meaning so that it will be easily understandable by the search engine,
In that term, it helps in SEO-score.