the second so far seems like a worthy second game. they reworked a lot of the game mechanics from the first one, the game itself is way harder though. The game is definitly solo viable but certain builds are group orientated (all classes share the same skill tree, you just get different starting positions and can take as well all skills from any class as long as you have the requirements in stats)

they made two huge changes regarding skills which I really like. Before you had to find or buy from the vendor a lvl 1 gem and by using you would level it slowly alongside you. The problem came when you wanted to switch later skills around or try out things, you would have to relevel a new one. In the poe2 they solved this by dropping uncut gems and you can pick which skill you want. The uncut gems are dropping close to your lvl, so no releveling needed

and the other big change is, before all your equipment had gem slots in different color and they where either connected or not. So if you wanted to have one skill with 5 supports skills on it, you would need to find/ craft one that has 6 sockets, link them all (which is one item that randomly rerolls all links and hope you get lucky) and roll the correct colors for the gems. Now they got rid of the slots, you have a gem menu where you can place them and add support gems directly.

and microtransactions from the first game carry over to the second game. but otherwise they are independent