Straight beveled blades can be sharpened quite effectively but there are some precautions to take. The original angle should be maintained and the back (flat) side shouldn't be messed with. A lansky sharpener is what I've used with success, but a seemingly razor sharp edge won't cut. A micro bevel has to be put on as well , it's a slightly different angel to the original bevel.
here's a link to the procedure.
https://www.tacklescout.com/sharpen-ice-auger-blades/