I just want to add on to what others said about georgian walls. The UB is just so so so so meh. Why not do something more noticeable, that will have a meaningful impact? All walls are built faster. or all walls are stronger. all walls provide extra faith etc,. something that makes you go wow, they are not someone who i will attack lightly. doing something like making all walls quicker to build compared to normal, so making your UB not as much of go out of your way type of thing, would be nice. I don't remember off the top of my head where it is at in the tech tree(if its the same as the regular ren walls), but moving it up sooner wouldn't hurt either if they are in the same spot.
i don't think i ever felt threatened enough to build them. the pacing of the game doesn't help either. I feel like i can quickly go form Med walls right into Ren walls in a short amount of time, and the urban defense perk feels like it is just around the corner, so close that i don't feel like using any production on walls anymore.(maybe basic walls if i feel like they could use a little extra protection or just to fire on something like barbarians)
i guess i should be fair and say, that the AI usually votes for city center boosts in production, so building walls is generally quicker than before, combined with the policy card.