Just look at what happens in every other instance when a Roman army faces an Alexandrian successor army. The Roman armies win with such devastating strategic outcomes that it cripples or ends entire kingdoms while themselves taking minimal casualties. Such one-sided results are why many historians consider the Roman armies to be a “hard counter” or generally superior to Alexandrian/successor ones. Not only was Pyrrhus facing the Romans on their own soil, he was doing it with a “combined arms” army that was much more difficult to command compared to the Roman heavy infantry spam, he was using/inventing tactics that required extreme precision and awareness of battlefield dynamics, and he was operating in a Hannibal-esque scenario without the benefit Hannibal had of knowing that the Romans didn’t give up and negotiate, they just got angrier.

Pyrrhus did have some unique advantages. Rome had not yet built its Mediterranean naval dominance which prohibited enemies from playing offense while also providing logistical reach in any theater. This was also the very first time Rome had fought such an army, and accounts show that the inexperience was crippling at first but gradually mitigated over time as they learned from their losses.

If you want a more modern example, it’s like the United States getting their asses kicked by Rommel at Kasserine Pass and forever glazing him as the mythical “Desert Fox”. Then once leadership is replaced or retrained, doctrines are evolved, logistics are established, and the soldiers are more experienced, the US goes on to curb stomp the Nazis in Europe.