I've tested your patch, which removes everything except Select and Deselect. Being able to actually do some of the previously exposed things in the context menu, would make the Outliner a bit more useful from a VSE perspective. Can't this type of entries not have any functions exposed in and executed from the context menu? Ex. renaming or batch changing Relative Paths to Absolute Paths could also be useful?

Is the strip type also the reason for drag and drop into the vse is not working?

Can't media(Movie, Image and Sound) data-blocks be dragged and dropped into the VSE either(they can be dragged and dropped into ex. the Text Editor)? Would this be possible?

If you want to quickly have some media files as data-blocks, then this snippet can be used: https://gist.github.com/tin2tin/0da859896432245fd15cfe960fdd9ee9, the Asset Browser needs to be enabled under Experimental Features first. Then select all the media files in the Sequencer and run the snippet, then the media files should show up as data-blocks under Orphan Data:

I didn't investigate any of this. Apparently, drag and drop doesn't have much to do with the context menu.
Hiding the unused context options is a convenient way to fix the problem.
Support options like Hide/Unhide, can be added separately.

For suggestions like dragging and dropping items, everything should be well described and defined in links like:
https://blender.community/c/rightclickselect/?sorting=hot
https://devtalk.blender.org/

And then directed to a developer working in the area.

I mention drag and drop to use since it was planned: https://developer.blender.org/T77408 And so was a working context menu for the Sequencer view type. I had a dialogue with the Dev about these things.

In many ways this is just another example of how new features are only implemented to serve the 3D View and the golden and unbreakable rule of consistency across the software is completely neglected.

https://devtalk.blender.org/t/gsoc-2019-outliner-improvements-ideas/7185/398