Two said "The theme didn't excite us as much as we would have hoped." I'm guessing this means that there is no way to save them and re-submit.
The NYT editors are saying that the theme as a whole didn't sparkle enough to make the puzzles work for them, so you won't be able to salvage them with the New York Times. For puzzle consideration, the theme is the #1 issue that needs to work well before an editor will consider accepting it. There are other venues you can try to submit these to and see what happens. The New York Times tends to be the apex on this kind of thing, but other places will accept more simple not necessarily as entertaining themes. You may want to pick another source (LA Times, Wall Street Journal, Newsday - Wed-Fri, Sun, Universal, USA Today, etc) and submit them there if there aren't any other major flaws.
As a tip, broadly solving these venues will help so you can study what they do accept and tailor a place that publishes what seems to be like your themes.
But another one said, "The wordplay felt a little open-ended for us." Does anyone know what exactly this means or how I "close the ends"?
This one confuses me (as a lot of the other "glittering generalities" phrases like I see in submission sheets). But I'm guessing you have some kind of word play going on that isn't exactly inductive towards your intended answers that can't exactly be fixed by rewriting the clues.
And are these boiler plate responses?
I'm sure the NYT editors get a lot of submissions and tend to run through responses to them as quick as possible. I'm curious about the second one, myself, along with what people with more experience might have to say about this one.
