There is also the very real-world consideration of: How do I hire people to maintain this beast? Sometimes, you have to bow to industry trends. Otherwise, you

There is also the very real-world consideration of: How do I hire people to maintain this beast? Sometimes, you have to bow to industry trends. Otherwise, you're one or two resignations away from being dead in the water. A Haskell solution might be svelte and easy to reason about, for a Haskell programmer. But you have to also be prepared to train new hires on all that, and you may not have that lead time.