If users are already having datalake kind of system which is generating parquet files, the use case to use Postgres to query the data itself is questionable. I think having Postgres way of doing things should be prioritised if you want to keep your product in unique position.
Can you elaborate on what you mean by the "Postgres way of doing things"? Also, what is wrong with using Postgres to query data in external object stores? It is a common occurrence for businesses to store parquet artefacts in object storage, and querying them is often desirable.
It depends. If you're happy with Databricks, etc. you might be good. But we've seen many users want the simplicity of querying data from Postgres for analytics, especially in case of JOINing both analytics and transactional data