Despite how unncessary dragged the battle Oda successful to delivered to impact of the battle which worth the epic battle of two men. Come to think again this probably the most fiercest battle Luffy had after time skip, Doflamingo hardly called as battle technically it were everyone vs Doffy while Luffy vs Kata is purely single battle. Hordy and Caesar more like warm up
Might to say battle with Katakuri is how Oda secretly drill Luffy before fight against the most durable creature in OP World; Kaidou.
Now i hope Oda also will give Zoro a good battle in future. He never have a strong foe so far after time skip.
Oda clearly put ego all around to BM crew, how Morganna confidently claimed Roger would not escape from their trap made me laugh
I don't think Luffy will go out from that mirror because Pekom is there then that mean he might has secured alternate escape mirror for Luffy.