I'm puzzled as to what more story they would have told had they been renewed. Not saying the show was bad, rather asking where would they have gone from here? When you've upgraded to moving anywhere in the galaxy instantaneously, you've traveled into the far future, rebuilt the federation, and you've conversed with aliens living outside of the galaxy, there isn't much "boldly going" left in the formula.
Kind of like when all the characters in an anime get too powerful (DBZ), and it gets boring because you can't raise the stakes any further.
It doesn't sound like they'd made it very far into the planning stages, if they did any work at all, but I rather liked the positioning of Discovery as Starfleet's "first responders," able to reach emergency hotspots instantaneously.
Alternatively, I'm still hoping for a deeper dive into the galactic politics of the 32nd Century.
You say "galaxy" like it isn't just a fraction of the universe. There is literally infinitely more to explore 🙂 More to your point, would the writers' room have been able to transform that potential into another season, bigger and more epic than the upcoming one? We'll never know now, will we.
Say what you will about the show (and I know you will) but Sonequa M-G has been a stellar spokesperson for the franchise. She's just so damn wholesome and enthusiastic to be part of Trek.
Besides the writing not resembling anything Roddenberry would've made, the bad acting and pandering were really off putting. I'm genuinely surprised it even got renewed 4 times.