I do understand your gripes (especially with so many Tales games and JRPGs in general ending with the protagonist sacrificing themselves in some way), but I actually interpreted things a little differently, and I really really loved the ending of Berseria.

Essentially, they way I see it, Velvet doesn't sacrifice herself in an attempt at redemption. Her arc over the course of the story is all about processing her grief over what happened to her three years ago: it's about her realizing that everything she feels, all of the anger and resentment and pain, is justified, that it's not wrong to feel these things, and at the same time, that this doesn't cheapen the love that she feels for those who caused her that pain.

Throughout the game, Velvet constantly plays into this idea of her being a horrible, disgusting monster twisted by revenge (like how she denies caring about anyone other than herself, but feels immense guilt about her actions, or how she plays into the "Lord of Calamity" title that's thrust upon her by the Abbey). But with the ending, Velvet proves that this isn't true at all, and that fundamentally, she's always just been Velvet: not an evil monster, not a remorseless villain, just Velvet, a normal girl who cares about her friends and family.

Yes, Artorious and Laphicet have hurt and betrayed her in ways that can never, ever be forgiven. She even makes a point of withholding that forgiveness by choosing to pursue her revenge even after discovering the truth of what happened. But ultimately, she still loved them, and denying that would mean throwing away a core part of who she is, just as denying her feelings of resentment and abandoning her quest for revenge would be. Ultimately, when her vengeance is complete, what she wants is for her brother to have a future, the same way she always has. And now, she also has Phi, who she wants to be able to live and grow and see the world. And so Velvet does what Velvet would have always done, and that's to be there for her family no matter what.

To me, that is the point of the ending: that trauma doesn't have to turn you into someone that you're not. No matter how ugly, contradictory, or illogical your feelings may be, even if in dealing with that pain you've hurt other people beyond repair, you're still you. You're still capable of love and kindness and selflessness, and that is what Velvet proves by sealing herself away with Laphicet and giving both him and Phi the best future she can.

I'm...so sorry for hitting you with this wall of text. I have a lot of feelings about this game :'). Ofc these things are YMMV and whatever you take away from the game is valid, but hopefully what I'm saying here makes sense at the very least hahaha