"Bad" is subjective, but as I stated, it's my opinion. It's not about work ethic at all; it's about your own values.

To simplify:

1. Reinforced behaviors become stronger, while others get weaker. Ultimately, I'm a behaviorist (ACT).

2. Work is a big part of your waking life.

3. If you spend that much of your life going through the motions, you're strengthening behaviors that may not be constructive.

4. When your situation changes, and you need those more constructive skills and behaviors, you may find them much more difficult to access.

That's a very functional lens. However, there's a deeper lens you can apply. I believe people feel most fulfilled when they're routinely acting in alignment with their core values (what they truly care about).

Phoning it in at work may actually be "workable" from an ACT standpoint if your personal life lights up all your values, and you are feeling completely fulfilled by friends, family, hobbies, etc.

However, I would venture that most people also want to feel that their work is giving them some feeling of intrinsic satisfaction, not just a paycheck. You can call it Purpose, Mission, Self-Efficacy, whatever you want. In my framing, people don't want to live in conflict with their values 8 hours/day.

But there's an even more basic argument that I would make: Life is incredibly short. You are hurtling toward death. If you're phoning it in, you're giving away your most precious resource for a small amount of financial security (and you still might get fired). You may find that when you hit 45 (or 65) you look back and weep for the decades you poured into something that you didn't care about, or even held in contempt.

You have to do what's right for you, but it's never too late. As someone who has admittedly phoned it in previously, I'm violently on the other side now. Regardless of how you feel about your job, I strongly recommend finding a way to give a shit, or getting out by any means necessary.