In the context of choosing monolith vs microservices first, it's a safe bet that we're talking about startups; in the other 98% of the market you don't have a choice because something already exists.
What? You don't think large enterprises also have to make these decisions?
Is there a large enterprise that exists in 2024 that doesn't already have existing software?
Is there a large enterprise that exists in 2024 that isn't currently building new software?