Without a requirements doc stamped in metal you won’t get 1:1 feature replication
This was kind of a joke but it’s actually very real tbh, the problems that companies have with human devs trying to bring ancient systems into the modern world will all be replicated here. The PM won’t stop trying to add features just because the team doing it is using an LLM, and the team doing it won’t be the team that built it, so they won’t get all the nuances and intricacies right. So you get a strictly worse product, but it’s cheaper (maybe) so it has to balance out against the cost of the loss in quality