I don't think anyone here will debate you if you claim that XIII is more "polished", but don't you think that's kind of a weird comparison to make?
People should really take out their blurry glasses and go play XIII again to be remembered of just how empty and limited that game was. When you are constantly funneling the player from start to finish with little to no chance for detour, of course the experience will feel more straightforward and less disjointed.
Does XV slip in some aspects? Of course, but just take a minute to appreciate all that this game has in comparison to XIII.
How many towns or settlements with NPC's did XIII have? How many dungeons, especially optional? What about the enemy variety? How many times were you able to ride a Chocobo in XIII? XV not only allows for Chocobo use in plains, forests, swamps, deserts and even the skirt of a volcano, but the Chocobo can also aid you in battle and hell, you can even attack while you are riding it, horse-fighting style.
How much character interaction was there among the XIII cast? Did it feel charming and endearing? Or even fun at all?
How many minigames/distractions/extra activities did XIII have?
Again, people are really, really forgetting how limited in scope XIII was. I enjoyed the game for what it was, and had a great time playing it, but I completely disagree that it captures the feeling of "Final Fantasy" more than XV.
From using the Chocobo in larger parts of the game, to the magnificent enemy design reminiscent of the older SNES games, to the beautiful homages to the Crystal/Prelude theme, to the lighthearted sense of humor, to the towns and settlements inhabited by NPC characters, to the Summons, to the sense of wonder. All of these evoke a more classic Final Fantasy feeling that XIII ever could.