I was expecting that presentation to be stuff you were missing, but the presentation is saying that essentially every feature they describe is implemented in PostgreSQL. Of the SQL:2011 ones, only one wasn't (temporal tables), and even the SQL:2016 features had partial support (with the summary slide at the end of other features they didn't do in detail having stuff that looks familiar in a PostgreSQL context). Do you have a reference of features not in PostgreSQL you are hoping to use?
This lets me materialize a view and then inspect deltas between refreshes, with history, and even update the materialized view from triggers and have those changes recorded in a history table automatically.
I know the feeling of having extremely limited time, i'm in the same boat. But I use Postgres every day with my startup, and we lean very heavy on the database (not by volume of data, just by complexity of the problems). I've reviewed a few patches that I wanted to see get into Postgres, and contributed to discussions on the mailing list. That's about the extent I am able to do at the moment, but it's better than nothing. More reviewers are never a bad thing.
This is a good sum up of useful modern SQL features: https://www.slideshare.net/MarkusWinand/modern-sql