As far as singleplayer goes, Entrenchment definitely made things easier. The AI was improved in some respects, but its biggest problem remains the same: it's still very bad at taking down heavily fortified planets, and starbases made it even more difficult to do so. As a result, it's not uncommon to see an AI continually banging its head against a wall and making no progress whatsoever (provided you built your defenses well).
The basics are pretty much unchanged, starbase just added more tools to the toolbox. The starbases are the really big ones, and like anything there's something to learn and master there, but it's not going to change the foundation of the game (though it does change a lot of the strategies you will use).
