I personally think this kingdom boost detracts from the players who've invested time and effort early on. Im not saying your boost is going to be a 1:1 equivalent, but if someone started day 0 and you come hopping in day 15, I think there's an inherent expectation you'll be behind. Who are the players that fall into this category?
Brand new players stumbling across the game. A boost and a kick out the door is detrimental to their experience, both the struggle and the learning. Its significantly more daunting to try to learn AND manage a big kingdom, as opposed to seeing how the mechanics work at a micro scale, without feeling like any learning mistake will be too costly.
Players familiar with the game just finding it again; having newfound spare time; deciding to rejoin, etc. For these players, dick around and find a community, and give it a go next round.
Are those points even valid? Idk