>We're moving to .Net, and I was surprised by how poor the built-in DB stuff is

Right now EF Core is probably the best ORM that has ever existed. What exactly is missing?

Although for performance you would probably reach for something like Dapper but that is not an ORM.

Well that was my point, either you're writing a lot of code yourself ("assembly"), or you use EF ("Python").

We're not used to something like EF, perhaps it would work for us. But debugging generated queries due to performance issues is something we'd like to avoid. For now the decision was made to not use EF.

I think you might find Linq2Db[0] to be the right fit for you then, which brands itself on being typesafe SQL in C#.

[0]: https://github.com/linq2db/linq2db