There is no such thing as manual testing, that is ridiculous.
No automatic tests ==> you should go farming or something, not do programming stuff.
How do you guarantee quality otherwise? How do you know your manual tester took its insulin hit? Humans are bad in repetition.
Ridiculous.
Manual "tests" are about getting the feeling on how it works, how approachable it is etc., not about feature correctness as it is described in the funspec.
But it's somewhat cross-purposes talking.
When people typically talk about automating the testing, they're talking about taking rote-based manual checks and automating them. Absolutely fine, no complaints from me.
But that's not automating "the" testing. It might be automated their testing, and those two things are different.
You can easily tell by whether they're doing it to get rid of the testers (cost-saving), or freeing up manual testers to do what they're good at: context-driven exploration of the problem space.
Flaky tests are mostly meaningless. Slow tests are burden.