Timestream has been in preview for too long. Does that mean they're having trouble with productizing it?

You can host anything in OP article in EC2 but you don't get the managed features. PLUS most of those (eg timescale and influxdb) are seriously priced for serious features like clustering/scaling/HA.

Plain Old Posgres is not awful for TS [1] but I'm also looking for something better.

At $work, we're considering Plain Old Elastic, which is a managed service. It scales well and if you don't have mountains of data, there shouldn't be surprises. If you do have mountains of data, and you can tolerate older stuff being slower in archive, you can throw it in S3 and query it with Athena, while keeping the faster stuff in ES or Dynamo.

https://grisha.org/blog/2015/09/23/storing-time-series-in-po...