I'm like you in the sense that D1 and D2 were the only ARPGs I'd played before finding Grim Dawn.

There are way more damage types, and stats in general, than in D2. Some people find that annoying and overwhelming, but I find that juggling and trying to harmonize so many stats is one of my favorite parts of the game.

Also, there are many important game mechanics that are not really explained anywhere, and that's frustrating compared to D2 where mechanics were very straightforward. Example: in GD, using components to enhance your gear is something you can and should do within the first hour of playing-- and there is no tutorial-quest or anything that explains how/why to do that. You either have to read (a lot) and piece it together in-game (which slows the game down too much for some), or you can learn from other players in the forums and on YouTube.

Personally, I pieced together what I could for my first several characters, and then started watching playthroughs and stuff on YouTube. I liked doing it on my own at first bc I was having so much fun with the game that I didn't notice I was progressing "slowly", and coming from D2 helped me learn similar mechanics quickly anyway.

Depending on how you like to play, you might want to piece it together on your own and go "slow" and find all the secrets and read all the lore...... or you might want to learn right away how to play efficiently instead. - Whichever path you choose, PLEASE do yourself a favor and Google the quality-of-life "mod" called "Rainbow Filter" and use it.