I disagree.
We, as technical HN crowd, know not to do this this. But any non-technical person who sees 'get a next-gen email addresses' being advertised for 9,99/year will expect more. A lot more.
Do not underestimate how naive and demanding consumers can be.
Very few new things emerge feature-complete.
Everything. All the time.
So the holier-than-thou, thou-shall-not-deploy-less-than-perfect perspective is pretty irrelevant.
This is a side project. That did something neat. The author should be commended, not lambasted for not rebuilding Gmail on their own.
And God knows the Internet would be a better place with a little more weirdness again.
;)
After all, people pay money to obtain these. Why anybody paying a subscription fee would expect that the product is useless?