EX Palen :
Well, Kilik got a clone with Xiba, so essentially I think that would replace Seong Mina.
As for Talim, I think Tira is sorta similar to her.

Yunseong was kinda like Xianghua, who was replaced by Yan Leixia.

Not all EXACTLY the same, but like I said... similar.... but even the "main characters'" styles changed a bit too.
I was a Mitsurugi player since Soul Edge and they changed up his combo sets a bit. I could only guess it was to try and make the new/altered mechanics flow a little better.

After the dispute between Natsume and Marvelous Interactive (I think? I could be wrong on that) concerning the Harvest Moon games, the company that had released the games in Japan as "Farm Story" gave the rights to their games away, so the franchise basically split into two: the original games now under the title "Story of Seasons" and Natsume making their own games under the "Harvest Moon" name.

Natsume released their own Harvest Moon game in late 2014, and I was very eager to try it... never had I been more disappointed within the first 15 minutes of playing it. The graphics were awful, the plot was dull, and the mechanics were weak.

Vanelan : Tira is nothing like Talim, and SCV wasn't her first game. Yunseong also wasn't like Xianghua, his fighting style was a lot different.

Kilik actually didn't get a clone in Xiba, since Kilik moved on in the plot to become the apprentice of Edge Master and a mimic character for all male fighters, and Xiba was introduced to be the staff-wielder Kilik once was. True is that Xiba has connections to Seong Mina through the backstory, having trained under her same master, but the naginata has always played a bit differently than the rod.

We also didn't get a replacement for Setsuka either, but I guess you'll say Viola for having such an unusual fighting style for the series (Setsuka used a parasol, Viola a magic orb).

Still, what matters is that some characters were left out without a proper reason. If we include the fact that SCV had three mimic characters instead of just one then the character roster has been heavily messed up, whether we had worthy replacements or not.

EX Palen :
Even though Talim (for reasons I could never understand) was a fan favorite, she wasn't particularly important to the story.
Setsuka did get a replacement with Alpha Patroklos.

They could have probably written better reasons, but a bunch of characters that were removed were non-essential characters.

I think the important thing is that SC5 was a solid game and the mechanics (albeit a bit weird at first) were done well.
In the end, it is a fighting game... most fighters have a story that sounds like a DBZ plot. "Generic fighter guy wants to be the strongest."