There's a lot of places to point the fingers in regards to Nemesis. But the foundation of it's failure did lie in the premise of the script. You can't just handwave in a villain like this and declare it intimate and personal without it also seeming forced and artificial. Tomalak and Sela, despite being able to count the number of appearances each had on one hand, at least had something of a history with Picard that you might have staged a personal connection with.
Suppose Tomalak was forced into early retirement because of his shaky history in the border incidents with the Federation. He blames Picard for this and is the focus of his revenge and desire for redemption. After he and a loyal group of officers manage to secure control of a few vessels and maybe an installation covertly, he launches an operation to steal Lore and reactivate him(I think the actor would've been available) as the perfect lure for Picard and company. It would've made more sense than being able to detect a random android a sector away.
So we have two classic villains, one wanting revenge for being shut down and the other wanting revenge and to display the Enterprise's broken hull on Romulus for redemption confronting the heroes. That might've been a fun movie and one full of personal connections and conflict with the heroes instead of a clone that "feels" like Picard and an android that fell out of a plot hole in the sky.