Batman 66 WAS Bad Actually (but not for the reason you think).

The problem is that for a few decades everyone had the wrong understanding of why it was Bad.

For the last decade or so internet discourse about Batman 66 has been about defending it because it's okay to have Batman stories that are fun and goofy and not so Dark, and I agree with that.  The problem is from my point of view there is no darker take on Batman then Batman 66.

Chuck Dixon who was born in 1954 recounted once on the playground when the show started saying in reference to it "that's not my Batman"  An eleven or twelve year old Batman fan in 1966 before any truly Dark Batman stories ever existed (even those early Kane and Finger stories are not what you've been told they are) would not have been saying this on the grounds that the show isn't dark and edgy enough for him.

Saying the show was faithful to the Comics of it's time seems justifiable on paper at first when you narrow down "it's time" to being not the whole Silver Age but the Jules Swartz era that started in 64.  The problem is a specific aspect of the tone.

You see Silver Age Comics could often be goofy and silly and dumb, and were often I think self aware of how goofy and silly and dumb they were.  But the core premise of the characters themselves was never the butt of the joke.  They were sincere, as were the Schumacher Batman films, and the Brave and The Bold Cartoon and the Justice League Trapped in Time animated movie, there was a core emotional resonance they each took seriously just like my favorite goofy and silly and dumb Anime or The Princess Bride.

The 66 Batman show was inspired by William Dosier and his friends laughing at the 40s Batman serials, not laughing with them.  They were not an affectionate parody of the comics but a heartless mockery of them.

A Batman who's response to watching someone die is to make a lame pun is far more of a cynical deconstruction of the character then any dark and edgy stories where he kills, because most of those take the concept of Batman killing seriously and have something to say about it, the message in Batman V Superman is that Batman should not kill, the message in Batman 66 is "who cares it's a dumb premise you shouldn't take seriously" they never even consistently kept track of it's Batman's attitude towards a criminal dying.

But people of Dixon's generation who didn't read the Comics or weren't as savvy to all this developed Nostalgia for it without actually understanding what it was doing as did younger generations watching the reruns.  And then as the fans who resented the show wound up getting what they wanted from Bronze Age and Post-Crisis alternatives that were visually Darker at the same time they slowly forgot the real reason Batman 66 was offensive.  

Then came the backlash to the relentlessly Dark DC stuff of the post New52 era lead by youtubers who only see cynicism and nihilism in scenes that are poorly lite with blood and scowling everywhere and so to them Batman 66 must be a happy optimistic Batman because it has bright shiny colors and characters who smile.