Does improving systems count as “research experience” in grad application?
No. Research is working towards creating new knowledge (not just knowledge that you didn't have, knowledge that is genuinely new to experts in your field, too) that advances the state of the art in your field.  

Programming/IT/engineering work is not research, unless it is undertaken to create new knowledge.

Examples: 


Writing code to simulate a physical system, so as to answer questions about its behavior that have not been addressed yet, is part of doing research. 
Writing code to implement a new kind of wireless communication system, so as to evaluate its performance, is part of doing research. 
Writing code to help me organize my students' homework submissions is useful work, but it's not research.