What you are pointing out makes sense, and I'm sure you could have written a much better script. Which is my complaint, the script sucks. The basic concept had a lot good ideas, but the execution was poor. So as I watch it, no, it doesn't leave me thinking that if they had stuck to the tone of the original pilot that it would have been a better show.
Actually my position is that the first season
was, in fact, a better show than the second and third seasons. The first seven episodes in particular -- four of which incorporate nearly all of the original pilot -- represent the best of the series, the point when it had the best balance of characters and hadn't yet been dominated by Smith. No, it wasn't on the same level as
The Twilight Zone or
Star Trek, but it wasn't trying to be. It was a kids' show. It was imperfect, but it was reasonably good, and certainly better than what came later. There were some good episodes throughout the first season. And there were a few decent ones in the early third. Most of the rest, though, is a mess.
I know you've watched the 60s Batman carefully; have you noticed the different tone in the first two episodes with The Riddler as the bad guy? For me that is a better example of the "pilot" (first episodes) demonstrating how good the show could of been.
The first two episodes of
Batman are a bit more serious than what followed, but I don't agree that was better.
Batman was a sitcom by design. The comics at the time -- or at least in the preceding years -- were quite intentionally bizarre and goofy and farcical; the Comics Code wouldn't allow them to be violent or dark, so they focused more on being fun and creatively bizarre. The show embraced that absurdity and ran with it, and at least in the first season it was one of the funniest, most innovative sitcoms of the decade. The pilot was more tentative than what followed; it didn't embrace the insanity to the degree that later episodes did. So no, I don't think it was better.
Now, I should make it clear that LiS is an entirely different matter. That's a show that started out as a fairly straightforward family adventure/drama with room for humor, then became more humorous over the first season as Jonathan Harris became the breakout star... and then completely retooled itself into camp in seasons 2-3 in an attempt to imitate
Batman. Changing yourself to imitate something else is almost always a step down in quality. But
Batman was always meant to be a campy comedy, because that's what the comics it was adapting were like in that era. So
Batman was being true to its origins by embracing the camp, while LiS was departing from its origins by doing (its imitation of) the same. And partly for that reason, what worked in
Batman (at least its first two seasons) was just embarrassing in LiS.
Interesting bit of trivia about the premiere episode, though --
Batman was originally meant to be an hourlong show, but at the last minute, after the first 2-3 episodes had been shot, the network decided it wanted a half-hour show, and so the producers had to cut those early hourlong episodes in half. So the show's famous 2-parter format with a cliffhanger in the middle came about pretty much by accident. Which is why the first couple of cliffhangers are rather bland compared to those that come later.
