Two and a Half Men's run can essentially be divided into 3 eras:
- Seasons 1-5 (2003-2008): The Golden Days
- Seasons 6-8 (2008-2011): The Divisive Years
- Seasons 9-12 (2011-2015): Rock Bottom
Then there's season 6-8, which aired from September of 2008 to February of 2011. These seasons are much more divisive. Charlie Harper (Charlie Sheen), who was portrayed as a womanizer, was portrayed as less of one in these 3 seasons. Some fans appreciated this because they felt it showed growth on the part of the show, while others did not react positively because Charlie's womanizing was integral to his character. Most fans, however, seem to agree that Season 6 is at least watchable, even the ones who aren't big fans of it. Seasons 7 and 8, however, are another story. If Two and a Half Men wasn't divisive before those 2 seasons came into existence, it certainly was now. Some fans felt that the jokes became much more juvenile in those 2 seasons. A lot of people felt that around season 8, while the show was still good, it was beginning to show its age and that it should probably wrap up soon. Little did they know Charlie Sheen was gonna go off the deep end and get himself sacked from the show in the winter of 2011 (To this day I still can't say "Winning" without cringing), and then... HOO BOY...
Lastly, we have the Ashton Kutcher era of the show, which aired from September of 2011 to last February, 4 seasons and 85 episodes of television that almost nobody is in the mood to defend. Most people seemed to agree that season 9 was just the writers trying to find their feet again and that season 10 would be better. I recall being absolutely ENRAGED by one of season 9's last episodes, but I decided to give the show the benefit of the doubt and give season 10 a chance when it premiered in 2012. NOPE. Not as bad as season 9, but still pretty freaking awful. Much greater emphasis on toilet humor, and every single joke completely missed what the early seasons did so well, capturing too much of the raunch and almost none of the wit. I don't recall which exact episode it was, but an episode from March of 2013 was what finally made me quit the show. The last 4 seasons were remarkably contrived. The show went from being about two brothers living together to being about a guy who became a billionaire because I don't know, buys a dead man's house because I don't know, allows said dead man's brother to continue living there because I don't know, without so much as requesting rent because I don't know. Then came season 11, which introduced Charlie's long-lost daughter Jenny, who he apparently knew about all along and just didn't say anything to his family about (Seriously, my 3DS is more lost than his long-lost daughter). I could just sit here and recap the seasons, but that's not what I'm writing this post for. I'm trying to figure out how this retooling caused the show to crash and burn the way it did.
Let's get the obvious stuff out of the way first. From the very beginning, Two and a Half Men's ratings were stellar. Within a few years, it had become the most watched comedy on television, garnering at least 20 million viewers every time a new episode aired. Not to mention that the censors were never very strict with this show. If you go on Two and a Half Men's TvTropes page and scroll down to "Getting Crap Past The Radar", it just says, "What radar??"
So what happened? Well, the obvious place to look is the changes in the staff. Charlie Sheen is a party animal in real life. His character, Charlie Harper was a hedonist. He was a womanizer, a gambler, a drinker, and the show was made with this persona in mind to contrast Jon Cryer's character, the comparatively humble Alan Harper. Ashton Kutcher is known for playing fun-loving, goofy characters, most notably Michael Kelso on That 70s Show. His character Walden Schmidt is also fun-loving and goofy, and is fairly immature in relationships always thinking that whoever he's with is "The One". Already the cracks are starting to show. Not only did the replacement actor have a completely different approach to acting, but his character had a significantly different approach to relationships, which are a HUGE part of what drives any show forward, even if it IS a sitcom. Just because an actor has experience in the sitcom genre doesn't mean he's suited to yours.
I suspect that the only reason Chuck Lorre kept bothering with Two and a Half Men as long as he did was to settle a score with Charlie Sheen (I wasn't sure before, but the series finale was what ultimately convinced me), but even so, I don't want to blame him for every wrong turn the show took. Even if he is the showrunner, I highly doubt one person could be to blame for everything wrong with a show. Nobody's perfectly good, and nobody's perfectly bad either. Not to mention that he wasn't the show's sole writer and most of the later episodes failed in completely different ways.
Not helping Two and a Half Men's case is the fact that it wasn't really even designed to run as long as it did. The show was about Two men and a kid at first, and if a show like that continues after the kid grows into an adult, the show has outlived its premise, which ALWAYS leads to a decline in quality. Seeing as the kid was only 10 at the start of the show, it had more leeway on that front than most shows do, but it still wasn't designed to run for more than 8 or 9 seasons. Full House had 3 child actors, so it probably could've kept going past season 8 if it wanted to, but even it dropped the ball on that one. Interestingly enough though, I think longevity may be one of the main reasons Two and a Half Men managed to maintain a following after season 8. When people get older they often have a sense of longing for shows they grew up with, and until recently Two and a Half Men fans didn't have that. Most TV shows that people become attached to as teenagers go off the air by the time they're adults and Two and a Half Men is one of only a few shows not to meet that standard.
The bottom line is that the majority of shows go through at least one of the things Two and a Half Men did and none of them is bad on their own. It just seems that Two and a Half Men was unfortunate enough to fall victim to all of them in a turn of events that I hope discourages networks from making these mistakes in the future.