It’s important to not copy content or use blockquotes according to Google. Rehashing people’s work does not make you rank higher in SEO. If you are going to reuse someone else’s content, rewrite and make an opinion on it.
A reddit user recently asked Google’s John Mueller how blockquotes are treated with their crawler and his response was:
“Google doesn’t treat “blockquote” or any of the other elements in a special way when it comes to quoting other pages. The important part is really just to make sure that whatever you’re publishing has unique value of its own. If it’s just a rehash of someone else’s content (quoting it) with no added value, then that doesn’t really leave a good impression, neither to Google, nor to users.”
Blockquotes are ok to use if you’re making a basis to an argument or it has some relevance to your piece, BUT Google does devalue content that is copied.
To find out more, read Search Engine Journal’s article here.