[DEPRECATED] Simple Classic Theme

Unfortunately, no. This was previously fixable by a editing a registry entry but Microsoft hardcoded immersive menus into Windows Explorer so we're out of luck unless Microsoft re-adds this as an option which is unlikely

I wouldn't call that a solid fix.

I tried it in a VM and it did not work  - unless it can replicated on another machine, I'd honestly put it down to a random occurrence. It's not the first time someone has said they got it working and shown proof, but mine and others attempts to repeat it had resulted in nothing. 

There's an old thread on Sevenforums where someone mentions a version of AVG from 2009 can bug out the context menus and it'll result in the old ones to show. I hunted down that exact version and tried it on W10 1903 just incase, and ofc, no dice.

In short; it's placebo. It might work on your setup and that's fine, but unless someone else can follow what you did and get the exact same results, then count it as a fluke. This is the only real chance at a fix as of now: github.com/rikka0w0/ExplorerContextMenuTweaker

HKEY_CURRENT_USER\Control Panel\Desktop\WindowMetrics

Consider please also installing Folder Options X. It will make the appearance of the folders much more classic.

A reg file with the settings is attached
t800.reg (318 B)

Because ExplorerContextMenuTweaker is only compatible with x64 Windows
Will do!
Might look into that later

Sorry, I'm just stupid. My executable is compiled as x86 so when running those commands it calls the 32-bit version of regsvr32. Will be fixed in the next version