Not all advice is equally helpful to all writers. Some pieces of advice aren't even equally helpful to the same writer during different stages of the writing process. Like using a satnav, always exercise judgment before blindly yanking the wheel and driving into the nearest lake because a disembodied voice told you to.
That said, I think both bullet points are useful. Complementary, even. While writing the first draft of my current WIP, at no point did I dwell long on whether my specific ideas had been done before, whether my plot dragged in places, what various people I know would think of my book, etcetera, etcetera.
Did I have doubts while writing? Constantly. From the antagonist's vague motivation and inconsistent behavior to major worldbuilding issues and the flatness of my prose, every problem seemed like a monster and I was armed with a stubby pencil and an eraser. But I did not let my doubts hold me back. I scribbled a circle around the scariest monsters for later review and moved on.
A couple of months later, I finished the first draft and was left with a story spread across three notebooks. Many scenes were confusing, cliché, or plain boring, but other scenes were surprisingly salvageable. If you squinted you could see a real story hiding behind the bad parts. The story I wanted to tell all along.
For my second draft I rewrote my entire story from scratch, using the events of the ten to fifteen or so scenes from my first draft I liked as a skeleton. I filled in the gaps with a newly made outline and paid special attention to avoid the traps in the first draft.
My advice, for you to ignore or accept as you see fit, is to write that first draft. You'll end up with half or maybe even a quarter of a story, but you can build on that foundation.