Agreed. The initial presentation of information in-game with the objectives presented one at a time and the rewards for doing so is excellent. The issue is that it's just a basic overview and to really understand the game, you have to join an alliance for quality, in-depth guides. A new player has very little idea what alliance has the best resources for this, apart from picking one of the top ranked ones. Then they don't do know if the culture is a fit for them. Additionally, the amount of information to read and absorb is overwhelming to a newcomer.
Today's PnW looks a lot different than the one I left a few years ago. There are API keys, bots and scripts for game advantages that are utilized by those with the understanding of how to do so. This is intimidating for a new player who wants to be able to manage their nation efficiently but doesn't have access to these tools or understanding of how to use/create them. The answer should not be to join an alliance that does. It should be built into the game.
I haven't even seen the mobile app. It's not available in the Apple Store although there's a link to it on the main game page. But, the game website needs to be better optimized for mobile. Part of it seems to be but then, for example, if I go to one of my cities, I have to slide the page around to see all of the improvements.
I don't know how well this would work, but I will say that communities are all over the place now. Alliance forums have always existed, as well as live chat. It used to be that everyone used IRC. There was the game channel and alliances had their own channels, but you were all on the same server and could hop around between channels in one place. Discord has replaced IRC as the most prevalent client now, but my alliance uses Slack, for example. So now I need to be in Slack and Discord. Other alliances may use one or both of these, or maybe they use another alternative. I can't keep up.
Another issue I see with new player retention is simply a fault in the design of the game. You begin protected for a couple of weeks but then if you don't join an alliance, you will be raided out of the game. I'm not advocating peace mode for tenured nations, but why not allow new nations to remain on beige until their ready to come out? After the initial 2 weeks, you could penalize their growth a bit or limit improvements (there's a wide variety of options to make this feasible) so that they're encouraged to find an alliance and leave beige but not force them to do so.
Lastly, the war system definitely needs to be tweaked. I'm glad this discussion on military changes has been started. I know the game has survived for just over 6 years and that's a testament to the dedication Alex has put into it, as well as the player support for it. But that doesn't mean the current trajectory is sustainable. War is the pulse of this game. It needs some work.