I disagree. I think failgold is good.
Often times something has an unintentional use -- this is true of many things in civ and in other games. It's not a sign of horrible design, in fact it can be a sign of good design, or fixing bad design.
Many of the most cherished strategies are "gamey" and were not intended by Firaxis.
- Spawn busting
- Using spies to revolt a city before attacking
- Trading resources for GPT
- Advanced tech trading
- Mass promoting units
- Supermedic scouts
- Worker stealing
- DoW unit teleports
- Begging gold
- The Great Wall
The list goes on and on.
But what's more important is many of these tactics actually fix what would be extremely weak if used properly. Espionage points were meant to poison water of enemy cities. Realize that's rly what they had in mind for it -- after all that's what they told the AI to do. So espionage points are pathetically stupid, but being able to time city revolts with an attack, can give espionage points SOME impact in the game.
Great Generals were meant to just give your units a bunch of exp, and to have super strong units, etc. (basically useless). Now with super medic scout we make use of what was a barely thought out concept.
Mass upgrading units = They probably didn't intend for you to upgrade a dozen HAs to cuirs the turn you unlocked them, but this gives the GM a special use, other than just being like inherently worse than GS.
Spawn busting = Barbs are really dumb. Some maps are going to generate 10x as many barbs against a player as others, and then those barbs have a chance of winning a crazy battle and ruining your entire game. Spawn busting this nonsense gives the player some tools to combat this random chance hell.
The Great Wall - Meant just as a way to stop barbs, but on Deity barbs aren't an issue, and you certainly don't care about that great general bonus..... so we build it purely for the espionage points and settle a GSpy super early, giving both the espionage system and the TGW a purpose to an otherwise purposeless existence.
This could spawn some off topic discussions : / but the point is it doesn't matter if it's intended or gamey or abusive or exploitative. What matters is whether it adds more than it takes away from the decision making process.
I don't think failgold is bad because it fixes the fact that only a few wonders are worth building on Deity because either you can't beat the AI to them, you dont have enough, big cities to make them worthwhile, or they're just overall bad and you've learned how to better use your hammers.
Failgold makes use of those wonders in another way, and it buffs the industrious trait, which would otherwise be pretty cruddy.
National Wonder failgold isn't overpowered, it's usually not as good as world wonder.
1. Most national wonders suck too, but unlike world wonders you have to complete it yourself at least once.
2. IF the NW is useful, then delaying it to collect failgold is costly itself. The only time I failgold a national wonder is when the city I'm planning on building it is currently busy, so I might get a few fail gold turns in.
3. Building the same wonder in many cities in a row for fail gold means you are delaying receiving the gold. If you build the moai statues in 6 different cities before completing it, the odds are your initial city would have received a greater return from building wealth and using it immediately.
If wonder failgold is exploiting how building wealth is weaker, how is building wealth not exploiting the fact that building beakers is weaker?... Because you're exploiting the fact that running your slider at 100% is stronger, because you can exploit how powerful tech trading is.
), but you could get some minor benefit 
(I once got 2.5K+ gold just by farming fail gold on the NE... with a non-IND leader)
)
