There is a reason rejection letters from publishers are often a generalized form letter, and this ties back to both of the above topics I discussed. When an editor has fifty rejection letters to send out after an acquisitions cycle, and is still staring at a stack of hundreds of manuscripts yet to be reviewed, it isn’t practical to send a personal message to every author.
When I set out on this journey, I swore that I would be different. I would send a detailed critique to every single author who’s work came across my desk. The reality is: there isn’t enough time. And then there are the works that ‘just don’t fit.’ There isn’t much to say in some cases beyond that.
Still, if you get one of these letters it does not hurt to ask for more information. I’ve actually built relationships with authors who have done as much in the process of giving feedback and answering questions for them. Some publishers might not be responsive to this, but I feel that asking for feedback on your work shows an interest in your own growth as an author; and I dare any editor to have negative words in response to that!