In terms of understanding the lore and the world and getting immersed in it, is it okay to play Divinity: Original Sin 2 without playing part 1?

What benefits would I get if I play part 1 first? Is it worth doing so or has the game aged too much?

I'd say play the 1st one anyway, as it's a fantastic game. I'm currently playing through it for the first time myself.

But I can't imagine there'd be a massive issue with starting with playing the second one without playing the first, you'll miss a few nods here and there probably but that's about it.

I haven't played OS2 yet but, honestly, I barely remember anything about the lore of the first one. It was Standard Fantasy World 101 with almost nothing to make it feel unique. I don't see why OS1 would be necessary at all. This game also takes place hundreds of years later, from what I understand.

No you don't need to play the first one, the second has some tidbits and stuff from the first one but overall you hardly would notice them except if you are a die hard fan.

I'm playing the second now, having played the first one before. I'm roughly halfway through number 2, and so far, I see absolutely no need to play the first one first. An analogy is playing later Zelda games having played earlier ones - you'll get some "hey, cool!", moments, but the game works perfectly fine standalone.