Not every single movie is a flop this year, only the expensive ones so far. If you take in $200 million box office, then you are a flop if you cost $200 million but a stunning success if you cost $20 million. With virus and theater limitations, that means the expensive movies are far more likely to become flops than cheap ones.
In Disney's case, at least, the story is slightly different because they have the Disney+ paid option. I remember Black Widow opened with $60 million from paid option alone, that is, 2 million subscribers paid to watch it at home. Let's say each subscriber represents 3 movie tickets on average and each ticket costs $10, that represents $60 million box office, though most of that goes directly to Disney, which should be helpful at reducing the cost ratio. That's still not much compared to, say, Black Panther, which earn $700 million domestically, meaning that people went to to theaters to watch it more than once.
In that sense, neither Black Widow nor Jungle Cruise did well: being that they have Disney Plus access, people who are scared of theaters should have watched it on Disney+ instead, rather than just skip it completely.
There is another possibility: people might simply be waiting for Disney/Marvel movies to go to free Disney Plus access within a few months instead paying anything for it. Before Disney+, when I wanted to see a new movie, I either had to go to the theater or buy the DVD 3 months later. I could also rent it, but that was more cumbersome as I had to return it. Now, all I had to do is wait a few months and it will be free. I'd take the free option for basically every movie, especially now that I own a big screen TV. I don't have to go to the theater, I don't have to rent or buy, I don't have to move a muscle, and I already paid for Disney+. It just seems like the easiest and most reasonable course of action.
I agree with ScarJo that Disney+ is undermining a movie's box office performance because Disney makes new movies become free on Disney+ rather quickly. Now, if say, a movie only becomes available on Disney+ after 3 months, and you have to pay $30 even then, and it will be many years before it becomes free on Disney+, then the box office will be protected like it used to be.