Frustratingly "solutions" like pgBouncer and similar do not properly maintain session state in transaction pooling mode and so commonly used features like prepared statements cannot be used, which is a non-starter in many cases.

Meanwhile, session pooling mode provides almost no benefit unless you completely disable connection pooling in your application, which then means you incur the cost of setting up a new connection on each request.

MySQL's ability to handle many thousands of idle connections without breaking a sweat actually solves this problem, and does so in a very convenient way, particularly in a micro-services architecture, and I really wish Postgres supported it.