Replacing isn't necessary, but we need alternatives. And that means independent indexing. You can alawys use more than one.

There are only 9 companies (crawling & indexing) independently: Google, Bing, Yandex, Baidu, Sogou, Mojeek, Gigablast, Naver.kr, seznam.cz

as listed here, with other search partners (of Google and Microsoft)

https://twitter.com/SearchEngineMap/lists

Disclosure: I maintain that resource and work at Mojeek