Faster than TS for a narrow use-set is a fairly low bar. But as you scale it's a bar you have to measure against the available talent from the market. You've got to weigh the cost of a developer who can pick up a completely new framework sight unseen versus the weight of a developer who has documented experience in a platform or technology you're already using. If you go full custom development you can get incredible performance out of literally any language and framework out there. But as your project needs to handle more and more scenarios, the number of developers needed to maintain it reaches a point where you're better off with Off The Shelf software despite it being slower and not specifically suited to your needs.

If you can maintain your Unicorn hiring criteria long term, maybe fully custom stacks are maintainable. For most organizations, they need to move to something that the average hire can maintain going forward. That means big name boring software vendors for the most part.