For me, writer's block is usually a case of "I don't know where to go next." So, the answer is quite simple. Write down what you want to do. Plan plot points ahead, bullet-point style. No need to insist on specifics unless they're important to your vision. Writing down nice set-piece ideas ahead of time and figuring out where to fit them into the plot later is also a decent idea. I like to also go out of my way to write down the next 5-7 scenes, what happens in them, and what order they happen in, so I don't have to juggle making large-scale planning decisions and writing the damn book. As for the specifics, I usually improvise and sometimes I get cool stuff that accidentally happens as a result.
But, as for the more specific complaint that "everything you write is trash now", I get it, man. I've been there before, where I feel what I'm writing is absolute trash and as far as can be from the high art I instead seek to produce, so terribly imperfect and amateurish, and a very important thing to remember is that most book development isn't necessarily linear. It's often better to simply get a basic scene that does the bare-bones function of moving the story forward done in one day, no matter how much of a foot-slog it feels like, than to agonize over it for a week in the hopes that you happen to come up with gold. Sometimes I come up with scenes that I simply don't have the mental stamina to write out the specifics of, so I literally just skip them once I've got the general bullet points of what happens down(only those important on the larger scale, not a play-by-play) and write on. Once I've gotten a complete, basic story, I stencil in the smaller details and sometimes rework some minor plot executions to get everything nice and smooth.
At times, with the way I write, the precise motives of my own characters are unclear to me until later on down the line—not to say that I had no clue at the time, I just couldn't verbalize the specifics.