If you're a software shop, hiring an army of consultants to build out core parts of your solution who will walk away when they're finished, you're doing it wrong. Success doesn't come from assembling piles of slop, it comes from putting together a team that will stick together to build value over the long term.
If you're an individual who wants to improve X part of themselves (fitness, musical ability, scholarship, whatever) then hiring a "consultant" (a trainer, a coach, a tutor, a therapist) is not only massively beneficial but almost an essential part of the process. You can easily measure the value you're getting from the consultant against the progress you're making.
If you're assembling highly complicated custom work on strict deadlines, hiring experts in that specific area of customization is pretty critical to consistently making those deadlines.
> How do you find them?
Connections, networking, and reputation, usually. MrBeast is lucky in that YouTube presents a good search platform; trying to find people who had made massive cakes before was probably just 5 minutes of searching and sorting by views.