1500 is too short. Some stories need more space than that. It's not a question of cutting what isn't needed. You can't trim Metamorphosis down to 1500 words. If you did, I'd rather read the long version. Having the limit broader, 1,000-3,000/4,000 allows people not to compromise their stories if they require the extra words. I've written about 200 stories in the past three years. Some of which have been published. Very few have been under 1,500 words. With a larger limit, you can do both. You can write a short story or a long short story. Is the issue that people don't want to read and provide feedback for something that's lengthy?
A good idea I've encountered in workshops is for the person who wrote the story to define, to some extent, how it will be work-shopped. Some people have thicker skin than others when it comes to feedback, so maybe the submissions could come with a short comment about the balance of positive to negative comments and where they think the story needs work. I've seen people get really upset before. Burst into tears, even. Some of the feedback I've witnessed has been downright brutal. Obviously we want to avoid that. There should be a balance of praise and criticism. Too much of either tends to, sometimes, disrupt the potential for improvement.
Personally, I want as much negative comments as possible. They are the most beneficial to writing. But I've been writing for a long time, and I'm used to it.