I have a htc one M8, and I have the same issue that you mentioned blackdogAC, but I found a new update to android 4.4.3, where htc gave us a new file manager... looks like they found their mistake...
Duke 157 is correct. I found "File Manager" in the app drawer after the 4.4.3 update. Using it, I can delete files from my SD card; ES File Explorer still can't.