In short: they decided to get as woke as possible in season three, killed what was a cute show.
Like many others I started watching this for Nathan Fillion, he always plays likable characters and the first couple seasons of this were just that.
Now, though, they have (and nobody should be surprised) made this into a platform for political correctness and virtue signaling.
The first two seasons were actually pretty fun to watch, come season 3 and every episode has huge political statements to make, even making a professor who believes cops are bad and corrupt and racist a main cast member. Black inequality righted? Check. Gay inequality righted? Check. Cops are bad and racist? Check. Cops should be defunded? Check. Who needs a good story when we can just do that instead?
Season 3 has been all about being PC about everything, being a social justice warrior about everything and, overall isn't the interesting story line we got in the first two seasons about a middle aged man who becomes a cop and the challenges he has to overcome.
So what happens in season 4 when "The Rookie" is no longer a rookie? Will there be a new batch of Rookies that our main character gets to impart his wisdom upon? Probably, and we'll get more political correctness and virtue signaling shoved down our throats since it will be made in 2021.
There are a lot of promises made with that first episode that we do not get any satisfactory explanation for by the last episode. This is not a good way to make me excited for any future seasons, it only makes me feel obligated to watch it again. I really believe it could have been written to give a much better cliffhanger at the end.
This show is what you get from people who have been listening to too much "true crime" podcasts and think they are creative enough to reverse-engineer several 'thriller' threads into a retconned mess.
There's really not enough written for a proper TV show, giving it a surreal "high school life play" instead of a developed franchise. For example, the material comfort of the plane crash survivors is never really shown to degrade. They say they've been out there for weeks, but they are never really uncomfortable; for crying out loud, they are still wearing clean clothes by the last episode!! None of them lost their suitcases, so they all had their own pillows, blankets, and even managed to keep their formal clothes clean after several months of being out there. I really don't think it is too much to ask for Showtime to hire some of consultants to advise on some of the base-level deprivation they would have faced. I suppose I could be biased because I've watched every season of Alone and am amazed at how skinny those people get after only a few weeks in the woods.