David A. Goodman wrote The Autobiography of James T. Kirk (2015), The Autobiography of Jean-Luc Picard (2017), and The Autobiography of Mr. Spock (2020). He has been been a dedicated fan of Star Trek, having also written for Star Trek: Enterprise, and he was responsible for bringing Seth MacFarlane aboard the Enterprise for a brief role. [via Trekmovie] It's safe to say that there isn't much he doesn't love about Star Trek, and his love hearkens back to The Original Series because of its originality.
The Fifty-Year Mission The First Twenty-Five Years by Mark A. Altman and Edward Gross included a quote from Goodman who spoke about how Star Trek stands the test of time essentially. And, though a big fan of The Next Generation, Goodman had some strong thoughts about the differences in the series.
"In a certain way, Next Generation, as big a fan as I am of it, pales in comparison to the original series, because it builds on something that someone had already created."David A. Goodman
As fans, we can see what he's saying, and it does make sense. The Original Series established the background for the entire Star Trek world. Without it, The Next Generation and all of the other shows after it would not exist. Star Trek set the standard for a different kind of science fiction that hadn't been done before, and some might say the magic of The Original Series hasn't been replicated.
The series that came after The Original Series had a foundation to build off of. They still had to figure out some of the rules as they went along, but TOS established a good portion of them, including the Prime Directive. The Federation, Starfleet, and starships all began in the 1960s. Though some fans prefer other series in the franchise to TOS, there is no mistaking that the show that began everything will always be THE ONE.