The more I think about the overall arc of the album and what lead to it, the more 'thanK you aIMee' showing up on TTPD actually makes sense.
First, I want to preface this by saying that everyone has things they don't 'just get over,' and anyone griping that Taylor should Just Get Over the whole Kimye business is just bored with it as a form of entertainment. She doesn't have to be over feeling it, or even writing about it, just because you're over hearing about it. /rant
But to my actual point: on TTPD Taylor talks about Joe as her consolation prize. About how long and hard she fought to keep that relationship going even when it was on life support and actively harming her for literally years before she pulled the plug. And at least some part of why she fought so long and hard has to be because of the story she had crafted and comforted herself with over the years - that all of the hell she went through in 2016 must have been worth it, because she came out of it with Joe. That maybe 2016 was fate, was the price she had to pay for true love, etc. etc.
To then end that relationship? To have to say 'no, maybe 2016 didn't leave me with anything important and valuable and sacred'? No wonder she's thinking back to it. Trying to still mine whatever good she can from it (probably that she is a lot more resilient now), but also still find a hearty "fucK you aIMee" in her, because seriously what the hell.