Just like everything else in the list of bad advice, it's something that most depressed people have already considered or tried, and either are unable to try it (for financial or other reasons) or tried it and it didn't work. People who have never been through that wringer seem to be under the impression that depressed people just need to get on some medication and go to therapy for a little bit and they'll be fixed. Would be great if true, and it is for some people, but definitely not for all people. Even if there is some unique combination that would work for any individual "hopeless case" (which is doubtful), there are just so many different medications and therapies to try, and most of them need to be tried for a few months before you're allowed to say that no, it really isn't working. And then you are supposed to keep your chin up and move onto the next one, and the next one. It gets very exhausting and demoralizing for someone who is already chronically exhausted and demoralized.
It's an especially evil piece of advice when offered to friends and family. Many depressed people lack the physical energy and willpower to put themselves through the psychiatric system, again and again, without any support. If I believed in hell I think there would be a special place in it for people who tell their loved ones to "seek help" when those loved ones are currently, by telling them, trying to seek help.
Honestly sometimes it gets to the point that I don't even want to spend time around other people unless they are equally chronically depressed, because you can't have an honest conversation with people who aren't. They either go into pollyanna mode or tough love mode and neither come from a place of actual connection and understanding. I think it's too scary for them to try to understand so they don't really try, and we get a multitude of platitudes that don't do anything except maybe make the giver feel better about themselves for doing a "good deed". If you explain why the platitudes don't help they usually just get mad. I think suicidal people spend more time doing emotional labor for non-suicidal people than the other way around. And then they call us selfish for leaving when we've finally had enough.
It doesn't sound like good advice if you're depressed, it sounds like an anxiety inducing platitude.