Good points, the BAR FAQ's first question is "Best Twitch Stream Settings for BAR (OBS)", and the Gameplay page talks about physics, terrain, economy, units and weapons but answers nothing like: is there a single player campaign? Are there AI opponents? what's even the theme/setting of the game?

Those are lowball system requirements too.

You can easily play or spectate a low-unit count game of BAR on any decent 2010+ quad core.

Such a computer won't allow you to play 8v8 that goes into the late-game stage. Sometimes not even 4v4 or 2v2 with players scaling to high unit counts. Some players try anyway. Ignoring player disconnections, half the drama of large-scale games is the one player who's lagging because they're on a potato computer. If the sim doesn't lag, the game will at least be down to single-digit fps.

That means you can't really play multiplayer comfortably, at least not beyond 2-4 players.

For that, you need a recent ryzen or intel. I'd estimate recent as post-covid.

I don't know what combination of things is important; there's larger cpu caches, faster sustained CPU frequencies (TDP and cooling matter there), hardware mitigations for speculative execution bugs, faster ram, resizeable BAR support... but in my experience going from a 6-core skylake-era cpu to a ryzen 9xxx, with the same gpu, made a massive difference. I saw no massive improvement going from a 4-core 2010-era cpu to a 6-core skylake-era cpu; I'd classify both as potatoes for BAR purposes.

My experience is the opposite: 0ad will lag on my laptop once thing become big. BAR will warn that it’s not compatible with my low end intel integrated potato gpu, but it works just fine..