I think this explanation is incomplete. There were still plenty of mid-size movies after the DVD era that still had profitable theatrical releases. The prototypical example to me is Baby Driver.
Pre-Covid there was simply not enough major weekends to release a big movie. They end up competing with each other.
Sure, Baby Driver made $300m on a $40m budget. But for pure profit maximization you are better off making a billion dollars on a $500m budget.