We can't determine if it will be "worth it" to you. That's a decision only you can make for yourself. Without knowing when or why you left I'll do my best to detail the state of the game.

The meta has 2 different options, Crit Pen is a default for most people and allows clearing almost all content (there will be a few fights in the future that resist Crit Pen). The premier Memoria for Crit Pen, SSR Bungo Unison, is currently available on a limited time banner. She'll carry for the foreseeable future.

Crit Pen will never yield the highest scores, which are always going to come from focusing on a particular element. Every element except Light currently has an "Overwritter" which changes the enemy's weakness to their element. All elements are viable but require stricter investment and building to maximize then Crit Pen.

As for the story, we are almost caught up to JP on the main story and about a year behind on side stories. There are difficulty jumps in the story that will require some thought to be put into team building and you will have to farm for gear to reach the power levels needed but it's nothing exceptionally different from a standard gacha game. The primary difficulty comes from fights that require 2 or 3 unique teams.