If that's the case, did Moonsinger, Kuningas & SirPleb, for examples, use this strategy in their high-scoring Sid games?........or perhaps a Great Library "Borrow", or Spoils-Of-War strategies to achieve the same effect?
Since I know you still come around Eman, I'll respond to this years young comment.
For her first histographic game she definitely talked about the AIs having no beneficiary and thus implying the use of military alliances for gold from AIs when some AI leader gets killed. That qualifies as spoils-of-war. I believe she likely did something similar in her 2nd histographic game.
Now, she couldn't achieve the same effect as trade route pillaging as in during times of peace. But, the Spoils-of-War strategies (e. g. loaning out money for gpt, then using military alliances with gpt which are expected to cancel in a reasonably low number of turns) end up more universal. From my old saves and my current games, I can or apparently have used Spoils-of-War with AIs that don't have an extra luxury or resource. And though perhaps I could give a city away or pillage my own luxuries and have done so in some cases to get more from AIs, spoils-of-war end up less complicated and also does not loose out on food.
Also, arguments like those that rysingsun makes never seem well-thought or true to me. I mean, if I have warriors and workers for trade route pillaging, first they use up their movement points doing that. Resource or luxuries can slip away in a single turn also, and the trading factor I think contributes to that as more likely to happen on Sid level. Also, my empire gets run by a Republic. It costs unit support to pay for those extra workers and pillagers. Of course, one can get back much more gold, but it's not for free.
On the other hand, if you have AI troops in your territory and can force the AIs to declare war on you, *then* use of gpt for upfront goods does work out for free.
The use of trade route pillaging even on Sid also sometimes I think can be a crutch instead of a honed tactic. By a crutch I mean something like a tactic which gets used, but kind of leads you away from a more optimal strategy. The Great Library makes for a better known example. Aeson identified it as a crutch I think in the Four Rules of Wonder Addiction article (he wasn't talking about a 20k game). People can use it on lower levels for technology, but it's not optimal for acquiring technologies in comparison to researching and trading. It can still be something of a crutch on upper levels if one can research a technology more quickly than AIs, since The Great Library can't get used to extract gpt from a tech leader who most likely has the most gpt from selling technologies to other AIs. Trade route pillaging is kind of like that when used for technological purposes in that unskilled use of it might be less efficient than trying to research while using it for other purposes, or keeping it in mind as a backup.