Nit: Gemini's highest yield is 6.9% on their Gemini dollar stablecoin[1], and the withdrawal delay is promised to be at most five business days which they were able to adhere to (not that that's not long, depending on what you expect, just wanted to quantify) during last week's LUNA crisis.
Reddit thread at the peak of the LUNA collapse: https://www.reddit.com/r/Gemini/comments/uowmrg/status_updat...
USDC on Aave, Compound, or Curve all seem much safer.
For example, on Compound, USDC only pays 0.82%, or 1.3% if you count the COMP token rewards.
Also I don't think you can invest just in USDC on Curve, you have to do a pool that exposes you to some other currency, although I think DAI is solid and Curve has a cUSDC/cDAI pool:
...but rates have fallen already, I guess everyone is fleeing to stables and within stables everyone is fleeing to USDC. Current USDC rate is 1.46% (vs. 2% for USDT)
Turns out I did find the right place, you just posted long-obsolete figures as fact without checking, in a thread where the actual values were the central point of discussion.