Part of your opinion comes from the caliber of what you're seeing. Most of the shows you mention were done by Warner Bros. for ABC, which was still a struggling third back in the late 50s/early 60s...and most of those shows weren't considered all that good even back then.
I have to disagree on several of Good Life's shows. Maverick, Combat, Cheyenne, Gallant Men all got at least decent reviews. Try
this for a typically respectful view of Maverick from a later critic. Even the self-deprecating goofiness of 77 Sunset Strip earned some critical kudos. Unfortunately, the shows don't stand up particularly well today, though of course each offers some watchable moments. And needless to say but I'll say it anyway, this is only my opinion and your mileage may vary.
In all honesty, what I mostly remember about The Defenders was its preachiness and solemnity. So I'm a little afraid to have my memories confirmed.
I don't want to sound purely negative on fifties and sixties TV. Whenever I see the Dick Van Dyke show, I like what I see a lot. Mr. Van Dyke was an appealing and physically talented performer surrounded by a terrific supporting cast. But too often my warm and fuzzy memories of old television take a drubbing when I actually
watch old television.
EDIT: These posts are starting to look like chapters from one of Tolstoy's lengthier efforts, but a few examples of what I'm talking about...
The color Honeymooners episodes hadn't been seen on TV for almost forty years, so I sampled a couple. I really really
wanted them to be good, so my old memories of Ralph and Norton yelping at each other wouldn't suffer too much.
Well, they weren't a crushing disappointment, though everything looked too pretty in color and the musical numbers were distracting and often uninspired. The Gleason-Carney chemistry still clicked, but much of the material sounded tired and cliched.
Another example...a particular episode of Gallant Men. As I watched the show it suddenly dawned on me that it was leading to what I remembered as a vivid and extremely violent battle scene.
So I sat through the scene. And literally laughed out loud. I couldn't believe that even my naive boyhood self had accepted this as anything approaching real warfare. The scene consisted of a couple dozen cheap extras in German uniforms running around some, then falling down (often not too convincingly) and playing dead. If the Italian campaign in WW2 had remotely resembled this farce, the Allies would have taken Italy in twenty minutes.
So no, sometimes it's better to let sleeping memories lie.