Obviously it's silly to drive to the gym only to run on a thread mill, but that's not what the article is about, it's about lifting heavy.
Lifting heavy can't be replaced with lifting a lighter weight many times, it trains very different things. And using rocks or branches is not a practical solution. If you can't get to a gym and can't afford to buy your own weights, a better way is to look into calisthenics. You'd really only need to buy a door post pull up bar or similar and you're set.