The "unit" in unit test does not mean your ENTIRE APPLICATION. Ever heard of scope!?

I am amazed how often people write overblown test setups, mock hundreds of unrelated services, just to test one tiny bit of logic.

That bit of logic could have been a pure function.

For that pure function you could write a dead simple unit test. Given that input, I expect that output. Nothing more, nothing less. (It helps even more if the pure functions only accepts primitives, like string and numbers, or very simple immutable value objects).

No I don't care that the service is used by another service, as your mocked interaction also doesn't test the service as a whole but you just assume the happy case most of the time anyway. You want to test the entire application? Let's not use unit tests for that but let's use a different kind of test for that (integration test, functional tests, e2e-tests).

If you write code in a way that easily allows for unit testing, your need to mock goes away.