My firm does some of the same as you describe - creates content for clients with supporting inbound links for their websites. We also do subsequent social distribution to our clients social venues and to our own.
We experimented with the automated distribution (and still employ it in certain situations), but have found that there isn't nearly as much engagement - which is what really matters as social signals if you're looking for SEO value.
Automated submission frequently misses images or picks the wrong one, totally skips video, and most importantly doesn't allow you to comment on what you're submitting - a key attention getter and response generator.
Yeah, it takes time, but so does good content, which is what it's all about.