Because depression-brain is the sneakiest, most treacherous little dick imaginable, depression will use the voice of whatever you think is cool and good to talk to you. If your depression wants you to feel helpless but you're a seasoned privilege checker it will use socjus logic https://twitter.com/scumbelievable/status/1349147372169928707
It will hijack your entire political and social framework and parasitise that to make you feel awful. It will make you guilty for being sad when you don't have "real" problems like oppression, or because your marginalisation means your sadness will last helplessly forever
Your depression voice will repurpose things that were legitimately difficult truths to learn about social politics and use it to frame its central idea, which is that you are helplessly, infinitely worthless and your suffering is both unavoidable and deserved.
You will think they feel bad because, well, didn't it feel bad at first when you learned how bad the world is to certain groups of people & people like you? No, it feels bad because it is telling you bad things about yourself!
"If you can't do anything, that's ok!" has that sickly sting to it because it's a fluffy, appealing disguise worn by the ol' depression proverb "you can't do anything". And the people making it a catchphrase know that.
The better way of expressing the sentiment is to say that people's worth is not based on how much they do. Everybody deserves to live without misery and torture. What you "can" or "can't" do is totally irrelevant to your fundamental worth.
Again you can easily be tricked into thinking it feels bad because it felt bad when you realised you were mentally ill. Generally speaking, things you tell yourself should not make you feel panicky, or smaller, if they are true. They might feel daunting, but "right".
Having mercy on yourself ("you tried to do things and it didn't happen - that's OK") is good. As is contesting ableism ("my boss can't understand why my depression means I get exhausted by socialising, and keeps making mean comments about me because I dodged the work Xmas party")
Treating overwork, burnout, stress and a lot of the frantic obsessiveness that comes along with anxiety does require comfort with doing nothing. But the difference is that it feels like DOING nothing, in the verbiest sense - making the clear choice to not do. And it feels good.
With this toxic self-care, toxic socjus learned helplessness logic, it feels like doing NOTHING, emphasis on the NOTHING. It is not a peaceful place where to do something was not necessary - it is a frantic, frustrated place where to do something was necessary and was failed.