You can’t just delete the photos via explorer, but there are ways to do it.
You absolutely can.
Step 1: Don’t have iTunes installed.
2: Plug in phone. Click the “Allow device to access photos” popup on the iphone when it shows up
3: Go to my computer. Find the iphone as external storage alongside your HDDs/USB/whatever other stuff you have. You can also click the popup that comes up on your computer but ONLY after accepting on the iPhone first.
4: Double click to open and navigate to the photos on the phone. Theres only one file path you can follow.
5: Copy, cut, delete photos as you would any other file. I tend to copy + paste to backup, then delete as a separate action incase something goes wrong during cutting and they vanish.
I do this weekly (ish) with Windows 7. I don’t know if you can do it with iTunes installed, but I know it works without.
Windows just treats the phone as external storage.
Note: accepting the permission to browse files on the iphone is properly important to iOS security – as such it can be a bit fiddly if you try to access the phone too quickly. Sometimes it requires plugging in and out a few times. Usually it works first time for me tho.