can't delete files from external hard drive WD passport

I have never had this problem before, so wondering if it's a Sierra thing?

I saw a few posts about this issue, but they were from at least four years ago with lots of discussion about NTSF files and the only answers I saw involved buying third-party software. Is this really necessary? If so (which would be incredibly annoying) - is it Apple's OS that is causing this issue? Why?

I'm trying to organize my files and drives after a chaotic few years. But I am prevented from deleting any files from external hard drives (WD My Passport external hard drives). In past discussions, there were issues with NTSF files or non-NTSF files. I have no idea how to tell if my files are NTSF or not.

Does anyone have any insights about any of this? Is it a Sierra thing? How to override the apparent block on deleting files from external hard drives? Thanks.