More modification than invention - Arwen, Glorinfindel - no big whup
What does somebody from the 10th Ward know anyway. ;-]
It wasn’t a substitution of Arwen for Glorfindel. In the book, it was Frodo who rode the horse and defied the Black Riders, not an elf.
If I hadn’t read the book, then when Frodo says he’ll take the ring to Mordor, I would expect Boromir to laugh and reply “You? You can’t spend a night in Bree without needing rescue! And you want us to trust you with an all powerful ring in Mordor? BWAHAHAHAHAHA!!!!!!!!!!!!!”
And everyone else would agree. In the book, Frodo is the main character. In the movie, he’s a runt that always needs rescuing.