I listed Atlantis because I really like plundering. There are arguably better FP generating buildings that aren't so costly to level up, but AM is just really fun! Double plunder on an Evergreen Express with a bunch of sleepers, nothing else in game gives a rush like that lol. Also the best looking GB, imho so it's bumped up for that as well.
Truce is one of the most underrated GBs, depending on what era you're in. I am going to aid guildmates and friends anyway, and if I save TT aiding for players in VF through SAAB, I get a lot of value by trading down the goods. I'm in TE, my TT is only level 4 or 5 and I've been able to build a whole bunch of higher level GBs without having to pay someone for the goods. I've also sold many sets of Arc and AO goods, some OF as well, so some months it's like getting 500-1000 extra FP for not doing much other than aiding and setting up some trades. When I sell goods, I accept any era that isn't Bronze Age and then either donate the goods to the guild treasury (usually what I do) or use them to help take trades of lower era players in my guild. No other GB at level 5 has given me that much value, and it's also value that helps out other players, it's win-win for all involved. I have also spend very few FP so far on the few levels it has, other players who wanted prints have largely contributed to it so far, even if I had used mostly my own FP to level it would still be very well worth it.
As for aiding, sometimes I will manually look for late game buildings, but even lately when I haven't has as much time to do that, aiding the top 10-15 players of my friendlist and guild still mostly gets VF-SAAB goods. I built Blue Galaxy recently and was able to get goods within a week by mainly targeting SAAB and SAM buildings to aid/motivate.
If someone is in the very late eras, TT is not super valuable and I think this is where the argument comes from that it's not very good, but if you're 5-6 eras down or more from the latest era and you're in a guild with late-game players, it's hands down the best goods GB.