They didn’t seem terribly useful, compared to other long projects.

• Maintain humanity under 500,000,000 in perpetual balance with nature.
• Guide reproduction wisely – improving fitness and diversity.
• Unite humanity with a living new language.
• Rule passion – faith – tradition – and all things with tempered reason.
• Protect people and nations with fair laws and just courts.
• Let all nations rule internally resolving external disputes in a world court.
• Avoid petty laws and useless officials.
• Balance personal rights with social duties.
• Prize truth – beauty – love – seeking harmony with the infinite.
• Be not a cancer on the Earth – Leave room for nature – Leave room for nature.

Basically, a freethinker version of the Ten Commandments tablets.

Openly advocating genocide and eugenics? Yeah, definitely not what I would call useful

If you read “Guide reproduction wisely - improving fitness and diversity” as eugenics and genocide, I think you might be jumping the gun a bit based on personal biases. Population bottlenecks require you to be very careful about species-wide gene pools. In a population of 10,000, you don’t want Cletus reproducing with his first cousin.

The only way you get a "population bottleneck" of 500 million from our current 8 billion is genocide. Even the world population in 1980 when these were erected was 4.5 billion. Still would have required genocide.

"Guiding reproduction" is definitely a euphemism for eugenics. Don't be naive.

Or nuclear near-annihilation, which was a definite concern when these were erected. Or a pandemic.