I'm curious as well. Because I've never complained about Trek being "too preachy".
Agreed. I think there has been discussion as to the differences in POV between TOS era introspective preachiness and TNG's finger-pointing, but all-in-all it is one of Treks endearing features. It is what focuses us on becoming better people which in turn leads us to becoming a better society. It has to be dreamed before it can become reality.
And peoples attitudes regarding Gene Roddenberry the man and Star Trek's preachiness are two completely separate issues whereby the former could be judged negatively and the latter viewed positively without those two opinions conflicting.