I joined the company pension comittee. Most large companies have an employee representative, its good practice. My company is under 500 people, so we're a bit larger then you but not incredibly large. An average member, since we have some very long term employees, is around $100k in assets. Once people start hitting 20 years, plan vaues get large.
On a plan with a total value under $50 million our fees are under 0.5% for most products. That includes producs that rebalance as you age, active managed funds, money market funds etc. Our money is pooled with other companies, its not like they manage our money seperate from the other billion under management.
A few years ago they switched up the plan to improve employee compensation, it was done to attract new employees. No one actually cares about you or me (don't be offended, just making a point here), but they care about attracting new talent, that's the driving force behind getting the pension revamped. So if you want a new plan, you need to work with HR to improve the companies ability to attract new employees, that tends to be a better pitch then worrying about returns for current employees. Would your company rather have an average plan or a competitive plan to pitch to new recruits?