There is no such thing as writer’s block, only writer’s aimlessness. The reason you can’t write is because you aren’t clear on the message you want to convey, not because you don’t have ideas.
Perhaps the prescription for writer’s aimlessness is the same as that for writer’s block—lower your standards and keep ideating. You might come across an idea that’s worth pursuing and refining. You might also discover that your original idea was plain wrong—don’t hesitate to abandon it for a better one. Remember that you should always have an end message in mind because the beginning and the middle can be formed around that end. If you don’t know what goal you want to meet with your writing, stop and figure that out first.