Never let your audience guess what you are trying to say, your writing should literally speak for itself. When your content has too many errors, it becomes difficult to read and understand. Although, one or two errors can be skipped by readers, but glaring grammatical errors can minimize the impact of your content. Also, it can make your writing difficult to read and digest.
And then there is the amount of time that it takes to create content with this software. I have had past experience with text spinners and although it might seem like a fast way to write content, it often isn’t! By the time you have chosen a piece of content (or multiple pieces of content to blend together), put it in the software and produced content with this software, you could instead have created content that Google loves.