(Long time TA reader, first time poster)
I (and my SO) have been reading TA together for some time now, and have also become dissatisfied with the story.
I don't personalize the story the way some people do - it's a fantasy story after all - so I don't come at this from a place of personal investment. I don't particularly care about the characters per se, but I do love a hot well-written sex story, and those aren't all that easy to find.
To me, the objection in later chapters compared to earlier chapters, is that the earlier chapters seemed to focus on Sarah's journey of exploration, pushing personal boundaries, the uncertainty around that, her vulnerability as she proceeds, how her and her husband shared that, the raw emotion and sexuality around that, etc. Combined with the author's ability to write a far above average sex scene, and that was a story to enjoy.
Now in the later chapters, we seem to be focused on Sarah in a repeating infinite loop of very similar sexual acts, and at the same time becoming a sadistic pig. She's simply becoming an unpleasant main character, and we're somehow to reasonably believe that this is naturally buried beneath some sort of sex addiction/nymphomania thing that she can't control even one tiny iota, every single time an obnoxious 300 pound fat hairy asshole shakes his cock at her - at the expense of her career, her marriage, her children, her home, etc.
Herein lies where the story loses me. Well, two things. One, the sheer unbelievability of the whole scenario, and many subplots within the story. Again, I get it - it's a fictional story. I liked Game of Thrones (first several years anyway), and I never truly believed a fire breathing dragon was going to actually show up in my neighborhood someday. But there are just so many instances of Sarah especially (but Dan also) just behaving in a manor that is simply silly and not at all even a little bit plausible. I won't list them all, but they've been discussed in detail. There are many examples. Sarah and her old boss. Sarah and the janitor at her workplace. Sarah in the scummy theater. The story loses some of its impact when the plausibility factor is near zero.
The second thing, is that the story has simply become numbingly repetitive. Lester waddles in, waves his cock for a half a minute, Sarah loses all reason and has 14 orgasms. Wash, rinse, repeat. Even her verbiage during the sex scenes has become repetitive. Another example, Dan being "frozen" the first couple or three times he sees Sarah getting fucked....sure, that's a solid story theme. But when Dan is frozen for the 3,592,145th time in a row....it gets hard to swallow after awhile.
A lot of people have talked about when the story jumped the shark, but to me, it was when Sarah left work and went to Lester's hotel....and then proceeded to get fucked in a pile of Cheetos. The two of us literally laughed out loud when reading that silliness, and in fact, that was the last my SO read of the story. She gave up at that point, so now I follow TA solo.
There were a couple of points earlier in the story, where the author touched on how Sarah 'got her way' when arguing with Dan, or that perhaps she didn't fight fairly or with honesty (the scene with her parents after the theater thing). That's an angle that I wish was explored more in the story. It could have explained Dan's actions more than the "Dan is a sad defeated pussy" that we're kind of left with at this point.
Thank you for the opportunity to express my opinion.