Like Sinn Fein and the IRA. Politically expedient “distance”.

Partly, but also the vastly different power dynamics of these situations. To most honest observers there usually is a side here fighting for a more "humane" cause, like opposing their own enslavement, or opposing the colonialization of their country by another for some semi-enslavement.

Wouldn't you agree these are generally "good" causes, unless you are the aggressor in that situation?

The inherent asymmetry of these conflicts, particularly in military power, leaves the "insurgent" side usually not much more choice than use cruder weapons and go for targets of opportunity that may involve a higher risk of civilian collateral.

Which is not a new dynamic, it's a very old dynamic that many militaries throughout history had to deal with when occupying populated territories hostile to them.