To go back to the OP, and troubleshooting the task of watching TOS. The best thing to do is try and have as much fun with it as possible. Some have suggested embracing the 60's vibe. Others say go for immersion in the series and acclimate. Or bounce around, starting with highly rated stories. Or focus on the story, and regard the production through the lense of a filmed stage play (that's a useful approach for Doctor Who, too). Pick and choose. Or choose neither, and don't torture yourself. For myself, I've gotten through some of the worst episodes of TOS by watching a little bit at a time. A couple months ago, I got through The Alternative Factor over the course of a couple of days. I think I watched 5 minutes on one day, maybe 10 the next day. 8 minutes the day after that. Eventually, I ran out of episode. I laugh my face off when I could. And I watched other things afterward, to forget or distract myself. Other episodes are a little bit padded; and I would get through them in two or three days. That's a great way to get through the worst or the most boring or average episodes, if one is determined.
Other than that, my go-to method is to focus on the story, and just have fun with that crazy 60's atmosphere. They're fun stories with a lot of crazy action adventure moments, just for the sheer hell of it. There's some surprisingly good fight choreography, although these days it's easier to spot the stunt doubles. But if you're not having fun, what's the point? Do something else that's fun, rather than force yourself to do something you think you have to do. Star Trek will still be around, and maybe later the time will be right for you and TOS will click.
