After spending some time thinking about it, the core advantage for Disney is not around their content portfolio (which is very strong) but their ability to get enhanced efficiency and enhanced durability of their IP. When they bought Marvel and Lucasfilms, they were arguably damaged IP portfolios. Disney turned that around because of their experience building long lasting brands (The Mouse, Disney Princesses etc). I should have realized this years ago but the main advantage that Netflix had over other competitors was their ability to extract more value from content due to (1) a larger subscriber base and (2) the ability to create content based on viewership data. This would allow Netflix to slowly consolidate less efficient content players in the market.
Disney is turning out to be a real competitor because they are able to enhance the value of their content in a different way, by creating long-lasting and expansive content portfolios. This also allowed disney to slowly consolidate less efficient content players (Marvel, Lucasfilms, Hulu etc). Now that Disney has launched its own streaming service and is starting to get into the same area code as Netflix in subscribers (95M for DIS vs 200+ for NFLX), the last advantage Disney has to catch up on is their distribution technology and UX. Those feel like very tractable problems to solve.
Previous to this, I've been sour on new streaming services (e.g. Hulu - which will be Disney owned by 2024, Peacock etc) but I think Disney+ is here to stay and both Disney and Netflix will be mainstays in the streaming market. Good news is that I think consumers worldwide will be able to support at least 2 online streaming subscriptions so it doesn't have to be a winner take all business. However, scale is very important to amortize content and delivery costs and with the emergence of Disney+, there is probably even less room for other players.