Interesting article and its great to get insight but it seems to be preaching to the choir.
It points out problems with supplies and professionals being core reasons as to why the rides wont be opening this summer, but for many people that wont matter. The general public will see the large, mostly constructed roller coaster at Sea World and wonder why they heard about that project first yet Dreamworld has managed to finished theirs before it. It's an unfortunately bad look for the theme park and beyond educating the masses, there is very little they can do.
For most people they will lose in the court of public opinions. Another shortcoming for a theme park that desperately needs attention and sadly people aren't going to settle for 'We're sorry for your less than stellar day, but be sure to come back in a few months when it's better!'
I still think the Easter opening is incredibly risky. Yes, things are dicey now - But we are on track to have 90%+ of the population vaccinated by the end of 2021. Easter will be most families opportunity to travel after the Dec/Jan school holidays and if international travel is open then I can imagine that a lot of families will be using that opportunity to visit overseas relatives, catch up with friends or visit their favourite international destinations and considering that the government has already insinuated that they will let Australian's out before letting tourists in then I imagine that there are going to be some quiet theme parks in Australia.