tl;dr: There are a lot of legitimate reasons to not plunder in game, but your sense of morality is not a good reason.
You know there are these things called "Goods Buildings" that will produce those quantities.
Goods Buildings - structures to supply Goods to a plunderer that do not take up space in the plunderer's city.
There are also several buildings like the "Shrine Of Knowledge", which are not too hard to acquire that will produce Forge Points.
Why not have both? SoKs in my city and take what I can from your city?
but most, if not all, empires that advanced themselves by pillaging others eventually crumpled
And pillaged cities fared worse. After years, decades, or centuries empires change and collapse. Don't be so quick to dismiss the positive lasting effects of aggressive empire on history.*
Besides, harming others really is not who I am
And today, plundering resources is considered to be a war crime.
I'm not sure that contemporary morality or rule of law is a particularly strong argument to use against an aspect of a game that is both well within the rules and explicitly encouraged by the game creator.
Morality is always a slippery slope. To wit,whether you spend money or not. you voluntarily playing this game is both an endorsement of the game and supporting the game. Hence, you are as guilty of any sins you choose to attribute to the game as anybody else playing the game.
Now from all the above, you might take it that I'm a rabid plunderer. I'm not. Gave it up years ago. Not because of morality or ineffectiveness, but the purely pragmatic reasons that I don't have the time, got bored with it, bad design in one city overstuffed with Aid targets making me dependent on the hood for help with Aid mixed in with the surprisingly effective notion that if I don;t plunder, it reduces folks desire to plunder me.
There are legitimate reasons to not plunder, but any reason that ultimately is based on 'it's not right' is both self delusional and self harmful. Self delusional in that it is part of a game: feel guilty when someone lands on your Hotel on Boardwalk and bankrupt them? When you take their Queen? Win the all in pot? Harmful in that it puts the player in a victim's mindset so many of the posters have in the Help I'm Being Plundered thread which leads to finding fault with the game and others instead of trying to learn how to avoid it.
Let me end on this for emphasis. Play the gane however you want. I wont question your decisions, but don't delude yourself that skipping some part of the game gives you morale high ground.
* Of many examples, I'll use just one aspect of just one example to illustrate my point.
The one example: The British Empire. "The sun never sets on the British Empire." Built on blood and conquest and exploitation, bitter wars over centuries. One could argue it still exists in much altered form and somewhat reduced eminence. I'll let a member of the Commonwealth opine on that aspect. Humanity as it is today owes a phenomenal debt to the British Empire.
The one aspect: From June 1940 to June 1941 TBE was the only serious combatant standing against the Axis. If TBE had not had the massive resources and wealth accumulated over centuries of empire they would have been swept away resulting in horrors best left to fiction.
Highly recommended: Winston's Churchill's Nobel Prize winning History of the Second World War is an incredible read from one of the only two Leaders to survive the war. Duantingly large, 6 volumes and once started you will not be able to stop reading. Be careful though, you may learn a hell of a lot. Churchill writes compelling history of the decisive conflict that still shapes the world 75 years later.