The comparison the Helldivers 2 is honestly a little disingenuous. Helldivers 2 had a massive install size because they used an untested loading optimization technique by literally duplicating assets to make the travel time of HDDs reading head shorter. They assumed this would help the 10% of people who use a HDD but in reality it did not. They also reduced the install size by 5x not 2x.
By comparison path of exile 2 has many many more high quality assets than Helldivers 2 which naturally take up more space. There’s really nothing egregious about the install size of path of exile 2 given how much content is already there.
I’m also sure they will take some optimization paths before release because GGG are much more competent developers than Arrowhead but even after that the size will still likely be over 100GB and I wouldn’t really expect less.
There are 100% options for gaming with smaller install size budgets like Grim Dawn or D2 or others. And these days game streaming is honestly very viable if you have a limited install size. The option I personally use is stacking up cheap HDDs for most of my games while moving ones I want better loading for on to one of my M.2s as needed.
I just wouldn’t assume that just because Arrowhead have some bad developers and could pull off a 5x optimization means that other developers have the same optimization opportunities. PoE2 is already rather well optimized, so this isn’t really an issue.