[0] https://falconframework.org/
[1] https://klen.github.io/py-frameworks-bench/ or https://github.com/the-benchmarker/web-frameworks
You want the complete opposite; have as many problems solved for you already with battle-tested ways to break out of the happy path when you need to.
Every sufficiently large Flask app becomes a half-assed reinvention of half of Django, except without the hundreds of thousands of eyeballs and man-centuries of bug fixing.
Personally I consider Django without any additional apps less complex than Flask with apps (or "plugins" in Flask jargon) to handle basic stuff like auth.
If performance is a concern, both of them are insufficient and I would rather pick another language like Rust, Go or even Java.
For performance, we are building some parts of our system with Clojure. It feels extremely well suited, albeit with some initial learning curve.