Is that just me or does AI always was so bad? It rarely builds new units, it rarely sends ground units into attack. Is that BE edition problem?

It depends on few things:
- in campaign the AI has different settings for each scenario, in some it does not produce new units.
- also in campaign the AI can lock itself when you load the game sometimes.
- in the custom scenario it depends whether the AI is set to 'land attack', 'sea attack' or 'air attack'. The first one is pretty aggressive on land, but the other won't be a challenge on land. You can check in the map editor which script is used for which player in the player properties.