Exactly. Reddit did one last year like: “We migrated from python to golang and fixed a bunch of non-performant SQL queries. It was so fast, isn’t golang awesome?”
I was once asked to migrate a Microsoft Access application to C#/MS SQL Server because it was too slow. I just added a few database indexes to make it an order of magnitude faster.
(They still wanted to go ahead with the migration, but that's a different story.)
I have about a dozen projects I’d love to tackle in this vein. (Not as low hanging fruit, but enough effort they’re languishing in the backlog.) we’ll actually be able to get to more those projects with agents and good specs