when do you actually need a message queue anyway

hey everyone im workin on a system where we have several services that need to communicate but not always in real time like when a user signs up we need to send a welcome email update a user profile in another service and possibly trigger some analytics events doin all this synchronously within the signup request is startin to make the initial signup slow ive been readin about message queues like rabbitmq and kafka but im not sure when thats the right time to introduce that complexity what are your experiences when did you decide a message queue was the way to go and what were the biggest benefits or drawbacks you saw