I'm not a cubs fan. I live in iowa though so I obviously pay close attention.
I personally just didn't think it was necessary. Rizzo, bryant, baez, conteras were enough of a core. Your bullpen for a stretch this season was the best in the majors. To me Davies and Mills have proven they are legit MLB starters. If you went out and got an ace, with hendricks davies and Mills you would have been in the thick of things next year.
Plus I feel like they did this to themselves because you cubs fans can correct me if I'm wrong but I remember them holding bryant back in the minors to get an extra year out of him and now his contract ran out at the same time as baez and Rizzo(Maybe??? I'm less sure if that is factually correct)
It just didn't seem necessary to me.