I am sorry but all theme parks shouldn't be open yet. I look at how we have done here in Ontario and ask why can't the US do the same. We just moved into phase 2. No theme parks open yet. Patios only are allowed as well as all retail. Our cases have been under 200 for a few weeks now. Again I ask why can't that be followed in the US.
In the few times I have read here, I have seen you say something like this more than a few times. The reality is that every country (and in large countries, each state/province/region) faced different challenges, and managed this differently. Look at your own country, where your province is second worst. Do you think it would be useful to hear people from PEI, or Manitoba, saying 'why can't what we did be followed in Ontario?' Your province went down a path, and now you are trying to find a positive outcome. This isn't a competition to be better, nor can anyone be superior because their country happened to be better than another (so far).
I have said it before: each area has chosen how to manage this, and is learning as we progress. The general wisdom is that the recovery in Europe will be slower than in China, other Asia, and the US, and that perhaps the stronger lockdowns were not required to reach similar outcomes.
I also believe that you said that your motivation for improved figures in the US was to go on holiday to a theme park? My motivation is for the world to succeed, and for each area to find the best path to a positive outcome. Of course there are things which could be done differently in the US, or which people find frustrating, or frightening. But I cannot tell people in the US that they should be like Germany (or Australia, or Taiwan, or anywhere else) As of this week, there are indications that higher cases in the US may not mean the same outcomes as we saw earlier this year. It's interesting actually to see the results in different areas, with different limitations/openings etc, and for us all to learn from this so that in the coming months we can perhaps react differently than in the first half of the year.
As to WDW opening, Europa Park reopening in May in Germany, and there have not been any reported outbreaks as a result. It is one of the largest parks in Europe, with visitors primarily from Germany, France, and Switzerland. So while I have no plans to visit WDW, I cannot say definitely that they should not open, if one looks at various amusement centres globally and the outcomes. (With the exception of brothels, as there have been slower openings and a few reported outbreaks)