The lower cost of a function call versus any microservice network call is a good performance advantage of a monolith. Monoliths also make refactoring code a lot easier. While in theory I agree about the spaghetti issue, in practice I haven't seen much of a difference. In part because microservices seem to encourage proactive overdesigning, and then the designs don't age well.
I also find monoliths a lot easier to debug. You have the whole call stack, and you get rid of a lot of potential sources of latency problems. You don't have RPC calls that might sometimes get forgotten.
Given the choice, I'd choose monolith every time. Unless, of course, microservices are needed for various other reasons. (Scale, the ability to distribute, etc.)
I also find monoliths a lot easier to debug. You have the whole call stack, and you get rid of a lot of potential sources of latency problems. You don't have RPC calls that might sometimes get forgotten.
Given the choice, I'd choose monolith every time. Unless, of course, microservices are needed for various other reasons. (Scale, the ability to distribute, etc.)