If you think that every MP game is long run game, then you are delusional. Since Endless Space 1, 9 years ago, there are only simultaneous turns multiplayer (and single player) in every their 4X game, and people play MP just fine.

It is almost certainly a design consideration when deciding how they wanted the game to work. While personally I don’t see it as much of an issue, I can understand why not the option of play-by-email or play-by-cloud having can be disappointing. However, the vision they had for the game must not have been able to accommodate those features, and tradeoffs must always be made as a developer. I would be very surprised if Amplitude for some reason did not want to include it if they could.

Will this impact the multiplayer scene? Of course. But if you ask me, 4X games are mostly single player first, and design and balance should be made with that in mind.

As for the comparisons to Civilization… well, this is not that game. If not having those features is a dealbreaker for you, then I am sure Amplitude will miss having you as a player for their game, but as you point out in the dev response you got, decisions had to be made at some point about what to prioritize, and in this case the MP had to suffer for the rest of the features the game offers.