I agree that mining ETH with 1660 or 1660ti doesn't make sense right now; better to mine another coin and exchange it to ETH with them.
As ETH is scheduled to switch algos soon, I would avoid choosing GPUs based on their ability to mine Ethash.
Lots of people been talking about an "near" switch to POS two years ago, and they were telling others not to buy GPU's based on ETH mining merits. So at least I'm certainly not holding my breath! Whatever happens, 1660Ti is pretty decent on ProgPOW too, according to tests from BBT and other sources.