It's pretty bad career advice. If you're an indie app developer trying to make a living developing indie apps, then you need to care about design. If it's not your career, then it's great advice.
A few years ago I had a need for an app which would allow an android tablet to play media when power was connected and pause when power was disconnected. Nothing like that existed (at least open source) at the time, so I dug up some ancient school project someone made for an android app back in 2010, updated it to allow media controls, and used it. I published it on fdroid, but I put zero effort into updating the already-then-outdated UI and never updated it again unless I had another need for it.
I wasn't getting paid for app development and design. I am not trying to get paid for app development and design. To the extent that having done this impacts my career, I think "bothered to create a custom android app for his personal project" says a lot more about me than "does not have a state of the art UI for his custom personal project app".
If people are turned off from that app by the outdated UI, I could not care less.
A few years ago I had a need for an app which would allow an android tablet to play media when power was connected and pause when power was disconnected. Nothing like that existed (at least open source) at the time, so I dug up some ancient school project someone made for an android app back in 2010, updated it to allow media controls, and used it. I published it on fdroid, but I put zero effort into updating the already-then-outdated UI and never updated it again unless I had another need for it.
I wasn't getting paid for app development and design. I am not trying to get paid for app development and design. To the extent that having done this impacts my career, I think "bothered to create a custom android app for his personal project" says a lot more about me than "does not have a state of the art UI for his custom personal project app".
If people are turned off from that app by the outdated UI, I could not care less.