Yeah that's the issue. Even if they weren't getting paid, they'd still have to choose Google for a reasonable user experience. And I don't see that changing. It's one thing for Apple to get into Maps, and it's another for them to get into search...
The big issue is Google's monopoly on english-language search, which together with Youtube gives it massive amounts of data on every person in the world, as well as giving it immense influence over public thought. I can see Youtube's monopoly ending (certainly, Instagram could have done it had Zuck not killed Instagram's attempts at long-form videos), but the gap between Google search and other competitors (only realistic ones are Bing and DDG) is immense, and probably insurmountable.
Apple has a higher market cap than Alphabet, Inc.
Apple makes so much money that they’ve given back more than 200B in buy backs and billions more in dividends, Google has yet to return anything.