I see both sides of this, actually. Each of the names you listed got into the business when they were young and most were cute back then (Joann Nesti not so much - but she was in during a different time). They had to know how it works and that being young and pretty gave them a leg up (pun intended) as journalists. Some may well have pushed older ladies out the door themselves. Now that it's their turn, they're pissed.
Is it fair? No.
But commercial TV is based on revenue and revenue is based on ratings. And, a good newscast with good-looking women often equals good ratings. Go too far and you get a backlash from (particularly) women. So, a news director needs to balance things.
Look, I've met some brilliant meteorologists and analysts of current affairs who weren't particularly attractive. And they didn't make it on TV. These days, more than ever before (thanks to HD), looks are vital in the business. You don't have to be a model, but you do have to be "presentable." This is nothing new, I saw it happen 20 years ago when I worked in the business.
Not only do older women need to be on the lookout for young hotties, but some men do too. And, the word "older" doesn't work that well here because some of the women in question aren't old at all. BUT, women usually aren't like wine and a 25 year old cutie who can read the news as well as a 42 year old (who once looked hot) is going to have the advantage. She asks for less money, looks better and draws more viewers in. This is the nature of the business and has been for years. They knew how it was when they got in because I did too. Yes, it sucks when it happens to you and I sympathize with their plight. But each of them has to know that they aren't going to be anchoring when they're 60. Old ladies just aren't the recipe for good ratings.
Now older men can anchor at 60. Yes, it's a double standard and it's a byproduct of human nature (an older man is authoritative). Any man who survives the business for that long is looked upon by viewers with the respect that goes with being "older and wiser". It's the "voice of God" thing. Women don't develop that over time. It's a function of gender roles in human society and its something that is ingrained in us to the core. An elderly woman doesn't get on TV with that "voice of God" authority that the right older guy can. That's just how it is and it's not going to change.
