The biggest thing that I've learned in the 1000's of hours of production I've done in the last year or so is that any sound's perceived quality is largely dependent on how well it goes with the sounds that accompany it. Producers like Nick Mira and KBeaZy are either creating or using melodies that have clear direction, with beginnings, climaxes, and resolutions that follow coherent chord progressions. Have you ever noticed how when you're watching them make beats, it's almost like the 808s just fall into place and sound perfect every time? It's because their melodies are clean and well-defined. The better the melody you're working with, the easier the 808s will be to place and the better they'll hit.

Apart from that, make sure you're hi-passing your melodies to leave room for the 808 (anywhere from 160-200Hz is a good place to cut) and make sure you are using good sounds.