The business as a whole should have policies in place, but if it doesn't, that is a direct responsibility of the people whom are charged with running it.
If the folks who lead to the neglect and dangerous conditions (and were negligent) have since left the company, and the folks who now steer that ship have demonstrated that the policies that should have been in place now are, and have cleaned house - both by getting rid of negligent people but also getting rid of non-compliant equipment and machinery - (see also: closed rides) then it stands to reason that it deserves the perception to change.
The park DID kill people. the park IS responsible for the incident and the conditions that lead to it, but THAT park is not the park that it is today.
As for those screenshots - let me sum those up:
Every park has a history of maintenance and safety until they don't. Dreamworld argued prior to the incident that they shouldn't need independent inspection because of how good their safety systems were. Movie World was a few loose bolts away from killing more than 4 people, and would have been tarred with that same brush. Don't just judge a company's history - judge it's people.
The guy is protesting the loss of the Sky Loop. I think we've heard from him here already. As for the ride losses - why is Rapids understandable, but log flume isn't, considering Sea World also closed their homemade log flume? Tower and Wipeout were both end of life, and Buzz was an ongoing maintenance problem for the park and lacked capacity (and guest interest)- All these rides are 'understandable' in context. The only issue is they happened all at once, but better to wipe the board clean and start fresh with a new team than to continue trying to band-aid things to keep them running and avoid the major capital expenditure the park desperately needs.
This guy is talking out his arse. He reckons Taipan is "a tenth" of the DC Rivals height. Taipan is 128ft to Rivals 200ft, but if his view is that being a hypercoaster is all it needs to be the best then i'm not sure I want to give any weight to anything else he says.
Yes, Dreamworld has an image problem, and with so many recent ride removals its going to take a little while to build up their core offering. Memory fades over time, but they also need to show what has changed and give everyone a good reason to return and see for themselves. The media doesn't help, but all fades in time.
All said and done, if Ardent were to sell to a new owner, even if the shareholders and management stayed much the same, it'd probably be an enormous step in convincing people things had "changed" even though they have already.