Watching TOS in full was very eye opening to how much current cultural memory of what that show was doesn't match what was actually in the show.
Personal example I believe is representative. I grew up with three movies we'd watch in this hacked-together Frankenstein of a travel van with a tiny TV: Dantes Peak, The Cowboy Way, and Mac and Me. I'm 100% sure these were picked up in the bargain bin sale.
I loved them all at the time, because at the time they represented all the excitement of a vacation -- none were great, and Mac and Me is objectively TERRIBLE!!!
I keep an ear out for these kinds of things. ST:TOS definitely hits this note, long and loud (there was a reason there were few seasons). So does ST:TNG, but its actually really good.
ST:TOS I highly recommend because it remains engaging/entertaining and is fascinating to see as a lens into the late 60s, but "good" it is not.
ST:TNG I love and I think is the better show but it shocked me too when I tried to rewatch in order after ST:TOS. The first seasons are not great! I really had erased a lot of it from my memory. I realize now that it's not until a couple seasons in that it became the show I remember, that show was lucky to hang in there long enough to hit its stride.