[RedCrowbar]

The paper seems to mostly focus on the quality of cardinality estimation (mostly driven by statistics) which is admittedly one of the frequent sore points in Postgres. There's been some progress in that area though (CREATE STATISTICS being a highlight).

[systay]

Which is arguably the most important part of a planner. If you don't have good cardinality information, it doesn't matter if you have fancy planner strategies. They'll be employed in the wrong situation, and won't produce the good plans we all want.