That is a myth Disney record breaking year 2019 they made 13 billion dollars with stuff like Endgame, Lion King, Star Wars, Toy Story, Frozen, Aladdin, etc. If Disney keeps the current sub count for a year they will make about 9 billion dollars, Netflix at its sub count makes around 18 to 25 billion dollars a year. If Disney studios is only using the profits it movies to fund its other movies then what they will make from streaming fine. If Disney was using funds from other parts of business to supplement the movies it does not matter the streaming service does it?
I agree Disney wants to dip in the theater and streaming pool together but the amount of money streaming makes is silly, there is a reason everyone has jump on the bandwagon now. The stream service model is a different monster you don't have to make profit from a single movie doesn't have to be profitable it just has to contribute to a person keeping the service and overall they will get that money back. It might mean less 200 million dollar movies and more 75 to 100 million dollar ones but then again. Disney has a back catalog and does need to be everything service so it can make more expensive shows and movies than Netflix.