It's more than just owning the ecosystem.
Apple only has about 15% of the PC market. That is still respectable because it puts them around 3rd, but almost all the other vendors are shipping Windows. Thus, simply owning the ecosystem isn't enough when Apple only owns 15% of the market.
The same thing goes for smartphones. Apple owns about 20%, which is very respectable. That is good enough for a solid 2nd, and 3rd is a battle for 5%. However again, Apple is going against all other vendors who mostly support Android.
In the end, Apple simply owning and closing their ecosystem won't kill anything because they don't own the majority of the market. What is really going to kill Flash is when Mozilla and Google stop supporting Flash. Chrome and Firefox own about 60% (if not more) of users. And why would they stop supporting Flash? Security and performance. Jobs said it years ago, and apparently he was right.
It's easy to be right when you own the majority of the ecosystem and you hate them. What that amounted to is Steve Job was right about he's going to own Adobe ass.