Yes, you can, but you may not want to.
People like to think that embroidery programs like they are vector (and for the most part the EMB format is), however, it isn't quite as easy. Depending on the design, how much you are reducing and the stitch types for the individual objects, that could potentially lead to some issues. All of this does depend on the design in question. Also, just because it's in the EMB format, doesn't in of itself mean that it is fill with pure object based EMB components (even if it was the true master file, if they used manual stitches (which some people, like myself, still use that tool). I have seen some people embed raw stitch files into an EMB file and call it quits (particularly in their passive aggressive need of showing up their customer that asked for the master file). And while the software tries to convert to vector objects, it doesn't always work and/or make the most logical decisions in what object it converts to as well.
This is just approaching it from just the design perspective, depending on the substrate that it is going on, the individual stitch object as well, may not want to take out from every single object etc and if you take out so much, may want to digitize it in object type. When people complain about stitch heaviness and there could be some reduction, there is usually also a correlation of that design being filled with tatami stitches versus satin stitches (and don't just convert tatami to satin and call it a day, there are different tools for different stitch types for a reason) or even could use run stitches as well ( alot of people prefer satin over run stitches, when it is actually better to use run stitches and yes, that includes better visually as well).
So while the short answer is "yes", there is a lot of other elements that go into that and still retain a quality finished product.