The game is like a sandbox. Imagine minecraft. Children play minecraft. Some people go into minecraft and spend a few hours building a cute little house. Some people put 1000 hours into minecraft and build circuit board replicas.

I think a casual gamer could complete the POE 2 campaign in 20-25 hours. Maybe closer to 10 hours if you follow character guide. The campaign is like the tutorial for the game. If you still like the game after completing the campaign, then you unlock the "The Atlas"/"map device" and that's where the real game begins.

I have not tried the shapeshifting character.

The POE 2 campaign has dark-souls-like characteristics. The game says you should press space bar to dodge roll out of boss attacks. Some of the boss attacks can kill you in 1 hit if you don't dodge. The boss resets if you die. I hate the Viper boss in Act 3 the most.