Dreamworld is still lacking a dark ride, a water ride, a second major thrill coaster, a second inverting thrill ride and an adults-only space like a bar. They're also lacking shows - especially shows that aren't for little kids.
Most importantly a second themed land. Rivertown is it. Goldrush, Rocky Hollow and Ocean parade used to be themed lands (even if they got a bit crap toward the end), and Ocean Parade is currently a dead end with a Big Brother set.
Dreamworld needs to replace Rocky Hollow with a new water ride. They need to fix ocean parade from the Wipeout plot around to Kevil Hill and completely remove Gold Coaster - which is a janky painful experience - and tightly integrate a new internal entrance to WWW - maybe using the land to weave coasters and slides together.
DW doesn't need to 'replace what was lost' because they also lost the chair-lift, the paddle steamer, the Tiger Island presentation, Thunderbolt, and ToT. They need to build out new themed lands and have a good balance of attractions for kids, families and thrill seekers.
They also need to remove Motocoaster and Gold Coaster - which is honestly more of an opportunity than a loss - They don't need direct replacements, but a second family coaster, and a second thrill coaster are definitely things they'll need.