I had the same problem when i watched tos.
I feel like the storylines were purile compared to the more politically-based ds9.
And it didn't help that I hated the captain.
See I find the politically-based DS9 plots a bit boring myself. Current political machinations are idiotic enough but the politics of imaginary future civilisations are even more tedious to me.
I suppose the DS9/TNG episodes I like don't involve those complex stories of the internal politics of the Klingon/Cardassian/Bajor worlds.
If you say that the TOS plots are all puerile perhaps you are not 'getting' them.