To really see how your strategy stacks up, you need to play the game in online multiplayer. It's more challenging but also more rewarding. It also has social aspects (make friends online).

Sometimes newer players will take off if they think the game is over or they're going to be crushed, which is sad. I once played a game where I was reduced to one or two planets and a capital ship or two (I had to migrate my home planet into my allies' area in order to survive), and I had a ball just managing my capital ship and helping my team, and we ended up winning after a long, hard, drawn out struggle in a 4v4.

The antimatter regenerator adds a regen rate of few antimatter per second, I think something like 6, but you can upgrade it. Thou I think TEC have the best antimatter regen with their culture upgraded bonus, it's not as much but affects all ships. Also lvl 6 ability of Dunnov makes TEC spam abilities like crazy.

Lategame advent is all about the capital ships more so than the other races. They have good synergy with eachother and ressurect can be awesome if you screw up. A game I played that really dragged out (granted it was against the AI) I was fighting on two fronts and one side got completely destroyed. I lost 3 caps with level 5+. I was considering quitting at this point but my other fleet had a high level mothership, so I just bought 3 new caps and used ressurect on them. If I recall, it didnt even matter if they were the same type as the ones who died.

People playing online will probably preach guardians. They can be borderline imbalanced with how they can keep a portion of the opposing fleet out of the fight.

I try to mix it up in lategame. Simply spamming illuminators forever isnt gonna work in the long run.