I don't know what your definition of 'fully interacting with enemies etc' is, but yes it is an ARPG, so you slay swarms of monsters and bosses. There are no dialogue options to convince them of their wrongdoings or question their purpose in life, even though a few bosses will become friendly NPC's after you beat them in the campaign.
I will say though, it feels more like a goal to tinker your character in such a way, through gear, gear upgrades and skill tree build, to be powerful enough to slay those swarms and bosses, which becomes increasingly complex in endgame (you must utilize every tool the game offers, some of which are quite obscure), but fun and rewarding to figure out, especially if you're not following any meta builds.
Also, compared to other games in the genre, PoE 2 blends in some Souls-like influences.
I don't feel movement speed is much of an issue with at least 25% movement speed (I think 35% on boots is the max).
As for mob density: in endgame you're in control to decide the mob density through modifying waypoints, precursor (tower) tablets and the atlas skill tree. This way you can 'juice' a map node by adding events, more packs, more rare and magic monsters. I don't think you're ready for the waves, the first time you open a breach
That last bit about the waypoint mods is a good piece of advice for everyone.
For me specifically as a warrior who went block and armour, it showed me I need to further double down on armour taking all the % increases.