It's also just a declining pool of viewers; at maximum you can have 15 million on a good night, and on a night where nothing is happening, it's down to 5 million. That's 1-5% of the country, and even then how many of those TVs just have it on for background noise? You have so many places where the TV is just set on FNC or CNN just for the sake of visual noise, and to try to talk a declining audience to switch to this 'new' network you associate with reruns and multiple programming directions, and you're not going to do that because you'll just get customers who are like 'put it on a REAL news channel' (or are in a place at 3am wondering what the hell a campmeeting is).
Also don't forget just how much FNC is just in so many routines. Fox News Radio is now the main radio news service, along with their features on even mainstream full service stations, so even if you're nowhere near a TV with cable, Fox is going to be on something. NewsNation has just one radio station, WGN, along with whichever leftover affiliates somehow decided ABC, CBS, FNR, USA Radio, Salem, or Westwood One don't provide a good news product. WGN has become the most mid station to ever mid and is run godawfully (their schedule page thinks Jim Bohannan is still doing his show in his casket, I guess).
And Fox has Fox Nation, MSNBC has NBC News Now, CNN has their app. At the start of 2023, I still cannot stream NewsNation on Spectrum or even in their app off wifi. Nexstar failed terribly at getting their ducks in a row before launching NN, and Perry's 'the web is a fad' thinking is going to come back to bite him sooner than later.