Does The Kostura Cannon Have Any Benefit?

YES!!!

It is probably the most useful "superweapons" in the game. While simply disabling/destroying ships and structures may not seem like much compared to the novalith (even though it is), its secondary effect is just as useful. Any planet impacted by a Kostura blast is treated like it has a phase gate present, meaning your ships can jump from any of your planets with one (in the same solar system) to the affected planet. This basically means late game the Vasari can bypass any planet they which and directly attack your capital or other valuable worlds without going through any planets in between. While you risk your fleet because this is usually a one way trip, if you choose your target well you should be able to cripple your opponent before he can recall his fleet from the front lines.

Kostura Cannon used properly can dastroy any size fleet.

Its the sweetest feature in sins

To elaborate in what GoaFan said, if you send a level 6+ marauder with the attacking fleet then you can send the fleet home more easily. The tactic then becomes much more powerful as you can attack basically anywhere with very limited defence possible.

A. Damages all enemy units in the target gravity well (bonus damage to structures)
B. Stuns all enemy units in the target gravity well (longer duration to structures)
C. Opens a phase stabilizer node at the target gravity well

Damaging everything in a gravity well?  Opening up any world to back door attacks?  Shutting down all planetary defenses for a few minutes?  All in one device?  This thing is scary stuff.

lol I see how you could be confused on its uses I mean novaliths seem so impressive nuking planets but to be honest the Kostura and the Deliverence Engine are far more useful just because of the massive flexibility that they have also one note while Kosturas do disable all structures and defenses for some time around maybe 5 mins starbases are only disabled for maybe 15secs along with all ships since otherwise it would just be imbalanced overall though it is an incredibly strong super weapon.

Novalith? Impressive?

If only.

Basically only on large multi-stars when TEC can beeline to it with their superior economic growth.  I can get a 2-piece novalith nuke operational within an hour if the map is good for it, and start blasting homeworlds.  Absolutely deadly.

Unfortunately, that's the best the novalith has to offer.  It's very much a superweapon you have to bring out with an element of surprise.  If the enemy has time to prepare for it, it's going to be a huge waste of time and money.  On the upside, you'll have missile weapons maxed out so you can quickly transition to a bomber swarm.