Earlier quoted context omitted.
I believe most of those are offered by Citus Cloud [0]. I know it's not the same, but you can spin just a single worker and essentially end with a faster PG than the vanilla PG. [0] https://www.citusdata.com/product/cloud
It starts at a minimum of 2 workers. And the pricing is steep too. The workers only operate on distributed tables so if you can't shard your data then you won't get any use out of those nodes, and sharding comes with its own problems. Citus isn't recommended unless you really need the size and want to stick with Postgres/OLTP.
You are absolutely correct that you have to shard your data to take an advantage. It's not equal to vanilla PG. It's an alternative though.