The biggest mistake for CW and UPN was jumping into the broadcast network business when the world was moving to cable channels. Local channels are good for news and sports. Not much else. If you don't have those you don't have any advantage over cable channels but you do have more expenses.
Local channels are actually good for a lot!
I don't know where you live, or how old you are. I'm not asking and it's none of my business anyway. But when I was a kid local channels were a great way to capture the local flavor. I grew up in DC. We lived on a hill right off the DC and Maryland border. Because of this, we got both DC and Baltimore TV channels. The fact that you had two different populations in those two cities, with different tastes, different attitudes, and different interests, made for different programing.
It was great. In DC one UHF indepenent would air foreign films, along with Ultraman, and Gigantor. Baltimore would air silent era versions of the Our Gang comedies, along with Tobor the 8th Man, and the Mighty Marvel Superheroes. Before the abomination known as FOX, the was Metromedia Channel 5 which would air the greatest collection of B/W films from the 1930s and 1940s, while Baltimore would air the film noir. Channel 5 was also kind enough to run the Three Stooges, the live action Superman, and of course Star Trek. No C, D, or bloody E. Local channels gave me my first exposure to Dr Who. And then there was Creature Feature, which would air the 1930s Dracula, the Wolfman, and Things to Come.
Local channels aired a lot of great locally produced stuff like Teenorama.
When I got older, 8 and on, the old man started to get nostalgic for the relations, which were spread out between North Carolina and Upstate New York. Holidays and in the summer, we were off to NYC, Pittslburgh, Jersey, Virginia, etc. Again all with different, but great stuff on TV to pimp Kotex, Fords, and Pampers. Hell I never heard of Perry Rodan until my cousin Earl and I watched it in Pittsburgh.
Local channels, like the local paper, gave people things to bond over. Local stations were the shit. Then came FOX, WB, and UPN, and television as we know it started to suck. Instead of airing good stuff to bering people together, these so-called networks provided the worst kind of stereotyoed TV. Sure there's Smallville, and Married With Children, but that doesn't excuse all the other crap these networks aired.
Local channels kicked ass.