TLDR:
If you enjoyed Remnant: From The Ashes, buy Remnant 2, simple as that.

Introduction:
Remnant 2 is just the first game BUT cranked up to 11 on every aspect of it's design, better soundtrack, more cutscenes, perks and skills for each class, better gunplay, refined mechanics over the first game and especially superior boss design.

Boss Fights:
In the previous game almost every boss was a giant guy with tons of health that just summons minions with a few melee combos to boot, in Remnant 2 the bosses are a bigger spectacle much like the Soulsborne boss fights who can hold their own without having to spam you with fodder, combined with a soundtrack to rival that of Soulsborne with all tracks being beautiful symphonies accompanied by crescendos so emotional you think the song will finish out the game, Remnant 2's boss encounters are an absolute treat to gun down.

Environments/Quests:
Much like From The Ashes, the sequel takes you to many beautiful and diverse locales all with a vaster enemy pool compared to it's predecessor and filled with NPCs and side encounters with a few familiar faces to meet. These NPCs and area design are of course procedurally generated making repeat runthroughs as interesting as your first. The area design is a big improvement over Remnant 1, fully taking advantage of the jump button and adding much needed verticality, jumping from roof to roof while getting shot from all angles in the gothic city of Losomn was a highlight of the game for me.

Classes/Builds:
In Remnant 2 there is a plentiful amount of classes all with their own unique perks and skills, you can equip two of these at once and are able to combine them with the bountiful amount of rings, the imagination is the limit with builds and optimising damage output.

Co-Op Play:
Remnant 2 much like the first game is best experienced Co-Op and it works exactly like it was in the original. The only thing to really mention is the addition of the whole squad being included in cutscenes instead of exclusively the host, I love stuff like that.

In Conclusion:
Remnant 2 is the definition of a superior sequel, it's just "more" it's more bosses, more armour sets, more guns, more incredible environments, more rings, more builds, just everything you'd ever want, and more.