Everyone's accessible.
What will separate you and help you excel in this business is the ability to find innovative ways to access people. Because once everyone figures out the last way to catch an artist in the studio, it becomes so popular the artist will switch up.
One way I always built relationships was contacting artists managers inquiring about what they charge for features and shows. I did promotion from time to time(this was in SoCal, mainly L.A.), knew other promoters, and knew artists looking for features. When an opportunity to make them money came across my table, I'd make them money, end up in the club, at the video shoot, or studio with them while making them money(which gives them a reason to keep in touch), then exchange info and start sending beats that they don't just brush off because they actually know the guy sending them.
There's a million other ways, just gotta be innovative and do more than the last guy who hit them up on twitter like "where do I send beats?"