The dominant strategies are either:
1. Colony spam
2. Starbase spam.
3. Do both (the best strategy, but also the one requiring the most commitment).
Building starbases non-stop can get tedious after a while for most people. You're literally spending hours doing the same thing over and over again. But it is in fact one of the best strategies and the way people win on maps with fewer planets to colonize.
Perhaps this was the developer's intent....