Totally. If you’re writing code, you should care about making it easy to verify that it works properly - not just now, but in the future. I’ve started viewing people who don’t believe this with deep suspicion - what are they up to? What are they trying to hide?
“I wouldn’t change the code just to make it easier to test” is a strange statement. “Just”?
Testability is a first-order concern.
It’s as important as making it run.
There’s no “just” there.