No, it ridonculous!
A) Yes, since the people watch Batman every time it gets either an animated tv show or a movie. Which (again) a really good Batman film comes out close to 15-20 years depending on the director. The Batman tv show from the 1960's was a pop culture hit, when the first Burton's Batman came out it was a hit (that was 1989) followed by the Batman Returns, then the Nolan's Batman came out and did much better making Burton's a classic.
B) The one thing the TV show and MOS have is SUPERMAN. An American iconic character that most people know of thru pop culture.
C) I agree with you that the show wasn't that great, but the show lasted 10 years. WB saw a financial opportunity and they exploited, compared to the George Reeve and Dean Cain's show, Smallville has been the longest Superman tv run.
Where do you get there's going to be JL movie? They don't even have a plan on how to get the JL on track. Moreover, Batman Begins came out in 2005 followed by TDK in 2008. Marvel pushed out IM1 and the Incredible Hulk in 2008 with hints promoting the Avengers. Marvel is on roll regardless if is not making the billions like TDK. The bottom line is that they are pushing for their characters from a page to the big screen.
WB is not pushing for any other DC properties, they could've done a WW, Flash and Aquaman film. They did a GL film, but the power to be were responsible for the GL bombing.