On that front, I bring good news (probably). What was the last game mode they added that was endlessly grindable? I think it was Explore. Everything else since then has been gated to some degree so that established players couldn’t simply race ahead with their more developed account. Whatever is coming in 4.5 (I didn’t get to take part in this beta due to real-life circumstances), I would be surprised if it were endlessly grindable for an advantage that end-gamers would find useful. I think it’s a lot more likely to be something like diamonds or chaos shards, where the devs control resource gains to more effectively manage the economy.
But the dev Q&A is tomorrow (right?), so maybe there will be something more than just speculation soon.
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Kingdom levels >10 seems a pretty safe bet.