I have a lot of thoughts about this.
I can understand both sides of the argument, people who don't want to spend $30 and people who think it's fine for that amount....often it tends to be related to how many of their family members can watch it.
Streaming downloads don't go by the same benchmark (1 ticket = 1 person viewing in theaters), so it is difficult to quantify.
I've heard estimates that overall Disney would need to make $300 million for this to be successful. That's 10 million downloads...a large amount.
However, Disney is also running into a few other issues. No one knows when theaters will open and also open AT CAPACITY. It's not enough IMO for them to be open to 25 or 50% attendance, and the hype for this movie will have died down significantly if there's another 6 months to a year before it can be released in theaters. The other issue is that they can't keep delaying movies, because then when the theaters open back up, there's going to be an over abundance of movies that might be available, and there's going to be people who still aren't comfortable with going back into the theaters.
IMO, expecting 75% of attendance compared to what it was a year ago, once this virus is mostly "over" is still going to be an optimistic view.
Disney may be taking this as a loss at the end, but will use this as an experiment to see how it might or might not work.
I've also heard that they could do the same for Black Widow and probably get a much better response, BUT there would also have been a much higher box office return being a Marvel movie, closer to $800 million to $1 billion expected, so a much higher hurdle on the home streaming side.
Personally, I'm single with no family in the house, so I don't really plan to pay $30 to watch a movie that I'm only mildly interested in, but that's just me and I hope Disney can pull even on it.
In general, I think we're going to see more changes to what the theater going experience is going to become in the next several years (it already had begun). I don't want theaters to go away, but they're going to be more niche and only for certain films, or to replay favorites, etc.