I think it's totally natural for a growing event to have to cut out some content. It's not a bad thing, it just means you're curating and screening content appropriately so we don't have to. Imagine them airing every American Idol audition every season? Just not going to happen. lol
And I mean, the community has to understand, and not take it personally. If you submit a track to a record label, you have maybe 5-10 seconds of their attention (if you contact them with a clean, brief presentation and catch their interest) before they have to move on. This isn't out of disrespect, elitism, laziness, or anything like that. It's because they're receiving hundreds (if not thousands) of submissions per day, and giving full human attention to every second of every tune would be literally impossible given the size of most of their scout teams. It sounds like you are getting to that point, submission-wise.
But that's great! It means that Open Mic is growing, and with its growth we get another strong source of curation other than whales and bots that is fun and full of talent and culture. I think that's something Steemit can always benefit from.