Not all stores are equal. Do not buy from the Mac App Store for High Sierra (they often require Mojave now). Instead, prioritize:
Original Issue: Blizzard dropped support for High Sierra in 2023, causing a "Version Malfunction." The Fix: Download the "High Sierra Legacy Installer" directly from Blizzard’s FTP (not the main launcher). This fixes the certificate expiration. Status: Fully playable, including ranked ladder.
Original Issue: Multiplayer desyncs on High Sierra due to network stack changes.
The Fix: Aspyr released a steam_network_fix.dylib. Place this in ~/Library/Application Support/Steam/SteamApps/common/Sid Meier's Civilization V/.
Note: The complete edition now shows as "Fixed" in the SteamDB history.