What was the advantage of building the Roman army in the decisive battle with the Macedonians?

The Macedonians fought in a formation called the phalanx. It was a monolith, bristling with long spears (sarissa). A head-on attack was practically useless and threatened with heavy losses. This formation was good on flat terrain, on rough terrain the phalanx could disintegrate, in which case vulnerabilities appeared.
Roman legions were more mobile, as they were divided into smaller units that could operate on any terrain. As soon as the phalanx lost its solidity, Roman units rushed into the gaps. And in close combat, the Romans were stronger than the Macedonians.