TOS I think, was very cerebral. Especially considering it didn't have the technology or the budget for special effects all the time. So it focused a lot on sci fi and story. Spectre of the Gun literally had a cardboard prop. Most of the good stuff was in the dialog which was pretty cerebral. I do think over time certain expectations change. I don't think everyone now want to see perfect characters in an utopia where modern day concerns are avoided and the plot of the day is always solved at the end of the episode (and then on to the next adventure). I doubt that format would work today like it has in the past. All of the shows had weaknesses and strengths, some more than others. IMO, in TOS the secondary characters hardly had anything to say or do. In TNG the characters were too perfect. Kelvin Trek, too much mindless action, not enough filler. DS9 is the only trek that struck the right balance to me.