I asked something similar in this thread:
https://forum.mrmoneymustache.com/ask-a-mustachian/new-401(k)-options-no-sp-500-(/msg128208/#msg128208Response, from salmp01:
The difference between the .24 fund and a .15 fund that you could get somewhere else is 9 basis points 1% of .09 = .0009. If you have 100k invested in the .24 fund the added expense will consume $90/year. So the added tax benefit of contributing to your 401k probably makes it worth your while to put as much as you can in your 401k
So, the difference between a .15 fund and your .5 fund would be 35 basis points, or .0035. So, on $100,000 you are losing $350 a year. My top tax rate is 25%. So, I save an additional $2,500 per year in taxes by contributing $10,000. If you are similarly situated, tax deferral probably outweighs the fees.
Trying to speak up is a good idea, but might not work. I asked about fees in our meeting and they said "the company pays all the fees" and I said, "no, the fees on the individual investments" and everyone was like "those are less than 1%, so don't worry about it!"