You can do a lot with LiveView and hooks. You can embed frontend frameworks if you feel the need. It really depends on what you’re building, your own hopes and dreams, and who your users are. “Complex features” is a bit broad . Many have built complex features with LiveView.

IMO I would try to build as much as possible with LV to avoid adding one more tech to my stack. If that is enough I would stick with it, if not then I would consider adding react for example. In my current job we have been using only LV for the interactive part of the UI, building forms, searchable lists and kanban lists to manage work flows.