To make your SEO text to be effective, it must not contain content wich was just copied from wherever on the Internet. It also means that even if a copywriter is working on many texts, each text has to be unique, different from the others. The biggest and the most common mistake is when copywriters are working with a huge amount of texts on a certain topic and start repeating themselves. In the worst case, a situation may look like this - a copywriter starts just copy-and-pasting a sentence or even a whole paragraph. This is a big no-no.
We have just finished working on My Sister’s Choice project - it is a company whose goal is to provide senior care services. Our copywriters had written new unique texts for My Sister’s Choice, but they did not use the texts from other relevant sites and wrote new ones by themselves, because a resource which is full of non-unique content will fall behind the filters of search engines, and they may even fall out of the index, which means that they may no longer appear in the search results.
The texts for sure have to be unique - it is a very important moment. But. if you find any useful content online, you still can use it - paraphrasing and using synonyms to change the text is OK, but not copying and pasting. You can always check your texts with an online services to be sure that you are using unique content.
The keywords in texts are also very important. We worked on keywords, meticulously creating them to allow us to clearly identify My Sister's Choice website in the eyes of search engines. We did this because well-chosen "keys" which, when used in the right places, can guarantee that the search engine will include a link to your site in all relevant queries.