Nice of you to mention developer velocity: it is
extremely important, and it's also severely impacted by things that depend on the framework having good performance, such as initialisation time, development-time performance (it's important to have a quick feedback loop), time required to run individual tests (important for TDD), time required to run the whole test suite (running it often saves developers time during refactoring), time required to compile assets, time for the CI/CD to run (important to allow quick and safe bug fixes and a fast process), etc.
Once your app stops being trivial, those things start adding up and people start talking about migrating to something else, breaking the app into microservices, or developing in-house tooling. All those things cost money. It might take a few months but it happens. And I've seen over and over.
Also, having horizontal scaling is definitely not easy for non-trivial apps. It costs money to the company, might require extra employees, and might put a hold on new features. And horizontal scaling doesn't help you with performance time or developer velocity.
Also please keep in mind that performance and developer velocity are not at odds. Most of today's "fast" frameworks are quite good when it comes to developer velocity: ASP.NET Core for instance is #6 on the Techempower framework and is incredibly productive.