It's very hard if not impossible to do predictions over century timescales. How relevant are 1926 resource problems to today? If you wrote your comment in 1926 you would be talking about rubber, fertilizer, coal, wood or oil, and 4 out of those 5 are mostly solved today.
At those timescales, mining the moon or Jupiter for helium might be realistic, so the limits of earth are no longer upper bounds.
I agree century timescales are tough, I'm not convinced 4 of 5 of your listed things have been solved.
Rubber has been replaced with oil.
Fertilizer has been replaced with Natural Gas that comes from the same place as oil.
Coal usage has been replaced/displaced primarily by natural gas, see above.
Wood, or deforestation, was a real problem in the 1920's, but many uses were replaced by plastics (oil) and natural gas. Sustainable forestry helped a ton here too once it hit the paper industry's bottom line.
Oil is certainly not solved, so we solved 4 out of 5 with the 5th.
Exactly -- that means that any analysis based on the current (as of 1926) 'reserves' or 'production capacity' for rubber/fertilizer/coal/wood would have been invalidated as soon as we switched to using oil instead. Imagine if instead of harvesting helium directly we find an economic way to split nitrogen (somehow, who knows). At that point, what you'd have to have forecasted would be the 'reserves' of nitrogen, which are functionally infinite.
We're definitely not mining the moon for helium, but might well end up "mining" the gas giants.