It's REALLY annoying to have an enemy commander escape and lock down another planet and basically you have no avenue to attack. You're forced to quit because it's a forever stalemate, while they have all available technologies. It's really upsetting.
I agree. In fact, a lot of people agree - there have been multiple threads already regarding this issue. However, Galactic War in its current iteration is a semi-roguelike with some mandatory tech, Orbital being one of those. You should always try to roam empty or "easy" system to build up some decent tech before engaging faction bosses.
If you have no avenue of attack, then you haven't gotten creative enough. We do need the Avenger by default though. Give us an army of Avengers and 300 Astraeuses loaded with combat units, and that's all you need. Not the ideal invasion strategy, but it can work. Check out this guide I wrote on invading a planet.
Well.....halleys could be alright, especially if it takes a lot of them now a days. But the AI might need to become a little more proactive if that's the case.