A lot of junior (and not so junior) engineers write bad tests. Each test is huge, with lots of irrelevant setup, and many assertions. It’s hard to tell which requirement is being verified, and it can break for lots of reasons. So they change code anywhere and lots of tests break and it’s not clear what’s going wrong. Yeah I can understand how people with that kind of experience come to believe tests are a waste of time.
When an application is tested from day one, it ends up designed for testability, and individual tests are succinct, often one liners. Testing feels easy and delivers a high ROI.
I think of testing as a fundamental skill, like learning good form in a sport like tennis. You can be self taught with bad form and do alright for a while. But pretty soon you’ll hit a skill ceiling and get left behind by those who got coaching and practiced their fundamentals.