I'm probably alone on this point, but I've always thought that the idea that Star Trek could and did talk about issues more than other shows is just....completely untrue. It's incredibly untrue today, and was even untrue in the 60's. It used issues as story fodder to tell interesting stories that weren't as loaded because they were abstracted into stories about the future and alien planets, but there have always been regular everyday shows (cop shows, law shows, etc.) that have been much much more relevant and forthright talking about issues. That's why I kind roll my eyes (mentally) when I hear this idea repeated over and over again. And a lot of those shows aren't that good.
At some point Law & Order became "ripped from the headlines" every week, and it was just too formulaic and sensational and I gave up on it. Star Trek, more correctly in my opinion, just uses situations that are vaguely analogous, which is more enjoyable. Any time they've gotten heavy handed and you can tell exactly what they're referencing and what they want you think...it suffered.
I mean, really...just watch shows like Daniel Boone (on at the same time as Star Trek) or something that seems like light fare, but they often did stories about race relations that far surpass anything Star Trek did. Yet Star Trek gets this reputation for "going there" that just isn't really deserved.