Right,

But just because it was a standard doesn’t mean it made sense as a standard. So when 99% of applications don’t care to adopt the standard, it really only makes sense to let the application space decide what to do with middle click and to fall back on the user’s system configuration if it’s unspecified (which can still be paste if you want it to be imo)

As someone who likes the middle-click to do mouse relative scrolling, I would be OK with this being configurable on a per-application level.

I don’t think it really makes sense as a “standard”. Blender will never use middle click as paste, for example.