I think manual curation is hugely important, as i believe one needs to read a post to truly understand if it deserves support and an upvote and what percentage upvote.
I've been lucky enough to have been spotted by some manual curators in the past couple of months and its been instrumental to my growth here. It also serves as a feedback loop, as the more these guys curate me, the more time and effort I put into my daily posts and engagement.
I can appreciate though that from your point of view manual curation can be very time consuming, so maybe a hybrid model, where you do it manually 2 or 3 days a week and on the others you could write a script to search out content by building a list of regularly high quality posters and setting a minimum word count amongst other things.
Big thank from me in Ireland to yourself and all the other manual curators. You guys are truly the lifeblood of our community oxygenating the Hive bloodstream.