Would I pick Postgres 15 over Postgres 8? Yes, any day of the week. But I would also readily pick Postgres 8 over most of today's databases (including e.g. the latest MySQL and MongoDB versions), for most projects, if that was the choice I had.
MySQL foot guns were mostly under control by 2010, and it was operationally efficient to manage a cluster of MySQL servers in diverse configurations with mostly-known boundaries to what could go wrong.
The Postgres foundations are the same today, but what you can build on top is very different today than it was pre-9.x.
This assumes you need replication, though. You can get pretty far without it, especially given how wide hardware you can get now.
> MySQL foot guns were mostly under control by 2010
Eh. :-) I think you would have to specify which footguns in particular.
Risks to the business are more important to me than my enthusiasm for a technology or product.
Also replication can be good for other operational reasons, such as zero downtime major version upgrades. Again depends on the business need/expectations.