All ESPN wanted was for the SEC to sign on the dotted line. The "SEC Network" was just another negotiation chip in the pile. I imagine it was one of those "sounds good on paper, work out the details later" things - and by work out the details, I mean put in the minimum amount of effort and expense required to keep the SEC schools from making noise. That means spending money to generate what content you do make during sports seasons, and then going to ground during the offseason. No reason to have Marty and McGhee doing shows in July; no one's watching anyway. Just run Paul Finebaum out there every day, do reruns of everything else, and ride out the sports winter.
And really, from a financial perspective, once they got the schools to sign, what's the motivation to spend money on the SEC Network that they don't have to spend? ESPN owns the SEC. Where else can SEC fans go? Nowhere. So why bother? So it makes sense for ESPN. And even in a world where one might think "they could do more content," the question is - to what end? What amibition can there be to "grow" the SEC Network into something bigger or more robust; what would be the vision for that? Where else can they go to unearth SEC fans they haven't already gotten? And if they try to grow casual SEC viewership, then they're competing with College Gameday, which already pivoted to chasing casual fans decades ago - much to its detriment. So ... wash, rinse, repeat.
This is all, of course, entirely my subjective opinion, but I just feel like the SEC Network is what it is and I don't think we'll see much change.