So I've decided that the best course of action for now is to just obsess over the few - very few - seedlings that I know I did plant. Like my one baby lupine. Someday, it may grow up to look like this.
I also have a dozen or so baby golden poppies, which should grow up to look like this.
Someone in a garden forum identified some weed seedlings for me from photographs I took. She identified a nonnative annual mallow (Malva neglecta) and a nonnative annual buttercup (Ranunculus muricatus). She also advised me that two seedlings were probably not weeds that I think probably are. One of them seems to be a filaree, but the other, I still haven't identified.
Oh well. At least my redbud tree is still growing well. I expect it to start losing its leaves for the winter within the next few weeks. But next spring it should be covered with flowers.
And my deergrass has sent up huge flower spikes, so perhaps I'll have more clumps of it soon. When this one gets older, it should look like this or this.
And the golden currant that I was so worried might die, because it had only three very tattered-looking, brownish leaves when I brought it home from the nursery, is now looking very happy in its new home. Someday it may even grow up to look like this.