Why not? You can for example detect, if something is P2PK, and then handle it. And in all other cases, you can just assume it as valid. Then, it will be compatible with the rest of the network, just like a downgraded soft-fork. That's why old nodes have no Taproot or Segwit, and can still follow the same chain. And you can do that too, and throw away the whole Script implementation, then hardcode just some patterns for P2PK, and implement only ECDSA, and nothing else.