I am that turtler in Lastman. Or actually all remainging empires are hiding underneath their systemshields. Everybody is equally quilty over here. Shieldless empires were slaughtered quite fast as they were unable to break through systemshields and warppoint ambushes while fleets warpped inside their homeworlds.
Last time i broke free i lost over 1000 ships and managed to destroy 3 systems. Before that i was only empire who hammer it's way through warpambushes into procteded systems.
It's indeed quite hard for each sides: Other side has stockloaded ringworld and armada of bases and legendary trained fleets awaiting and outside lays 4 empires, covering 3/4 of galaxy (two talismans) guarding the gates. If/when i break free it's just another systemshield with warpambush, or ringworld system that is instantly recolonized after glassing, or ringworld under construction with solar bomb awaiting for fleet to arrive.
SEIV combat mode indeeds makes games stall in the endgames. Fleets are enormous and starter gets an huge advantage so combat gets quite difficult. So each side can't afford risk of attack and losing fleet and allowing opponent roam free for awhile.