I really think starbases need a buff. Their original position as "king of the gravity well", due to size and armaments has really eroded, thanks to the addition of Titans. But I'd also like for turtling to become a viable strategy (definitely not happening anytime soon)... counterable, but viable.
Anyway~ I agree that defenses should only hold off an enemy fleet to a point, otherwise they'd just be overpowered, but I also think they should hold on longer than they currently do against Titan backed fleets. Even the Loyalists and their two starbase upgrade only hold off a fleet boasting a Titan barely long enough for the defending player to funnel in reinforcements. The other faction's starbases simply get crushed too fast, regardless of the credits invested in their static defenses, for them to send any sort of defense fleet. I mean, static defenses are supposed to help support a defending empire's planets, not roll over and feed their capships/titans lots of exp. before help can arrive.
So if starbases, being the end-all-be-all of static defenses, get an overall upgrade to their durability, then maybe late game strategy would be a bit enriched.