I certainly feel that: TNG, DS9, VOY are the best of Trek [and TV in general...]. Those three shows contain the best acting, the most intruiging storylines & the most mature writing.
Did you see actually see TNG Seasons 1 and 2?
Great storylines and mature writing. Are you kidding me? Yes it got better.
How about "SubRosa", "Threshold", "A Fistful of Datas", the boxing Chakotay episode.
I think you're admiring the writing because it has a sort of sameness - consistency to it. You know whats going to happen next. Which can be a strength and a handicap.
I suppose TOS only had a bunch of hack science fiction writers for its stories.