Skipping the middleman is necessarily better because it is inherently lower risk for an absolute guarantee of 33% more upside.*
Investing in something else with even 16% promised returns, let alone 1500%, is not necessarily better because it is almost certainly higher risk.
* When Anchor (Luna/UST) crashed both StableGains and direct users of Anchor suffered the same percentage losses. But direct investors in Anchor had balances which were necessarily 33% ahead of StableGains investors due to not having StableGains shave off their interest earnings.
Stablegains had nothing going for it, in fact it had all of the risk with none of the reward. 1500% APYs are usually attached to LPs carrying huge risks of impermanent loss rather than stablecoin staking and are usually very transient in that they evaporate within hours.
FWIW I disagree with Anchor being termed a ponzi.