This is a common misconception. The total amount spent on the Apollo program over its 13 year time span (1960-1973) was $25.8 billion as reported in 1973, around $240 billion inflation adjusted. That's around $18.5 billion per year, distributed on a bell curve. NASA reached it's minimum post-apollo budget in 1978 at $21.3 billion per year! Their current budget is $25.4 billion. [1] So based on current (and historic spending) NASA could have been constantly doing Apollo level programs, on loop, as a 'side gig' and still have plenty of money for other things.
The modern argument is that we spend less as a percent of the federal budget, but it's mostly nonsensical. The government having more money available has nothing to do with the amount of money being spent on NASA or any other program. It's precisely due to this luxury that we've been able to keep NASA's budget so high in spite of them achieving nothing remotely on the scale of the Apollo program in the 50+ years since it was ended.
The big problem is that after Nixon defacto ended the human space program (largely because he feared that an accident might imperil his reelection chances), NASA gradually just got turned into a giant pork project. They have a lot of money but it's mostly wasted on things that people know aren't going anywhere or are otherwise fundamentally flawed, exactly like Artemis and the SLS.
The modern argument is that we spend less as a percent of the federal budget, but it's mostly nonsensical. The government having more money available has nothing to do with the amount of money being spent on NASA or any other program. It's precisely due to this luxury that we've been able to keep NASA's budget so high in spite of them achieving nothing remotely on the scale of the Apollo program in the 50+ years since it was ended.
The big problem is that after Nixon defacto ended the human space program (largely because he feared that an accident might imperil his reelection chances), NASA gradually just got turned into a giant pork project. They have a lot of money but it's mostly wasted on things that people know aren't going anywhere or are otherwise fundamentally flawed, exactly like Artemis and the SLS.
[1] - https://en.wikipedia.org/wiki/Budget_of_NASA