Honestly I think AoE4 and the community it has fostered may very well be the best we can get in this day and age for RTS games, and it has been great to see the continual development, additions and changes that have only improved the game since launch.
However, I think more than anything, the most important thing that can be done for this game and for the longevity of its community, is a proper in-game editor that can be widely utilized by the masses for minor use cases as easy-to-build scenarios, a way to playtest battles between individual units or masses of them, a way to place buildings freely and construct actual cinematic and real looking cities/places. Being able to change the UI or add models. The ability to make mods that can be applied to actual games. I’m not going to go into the other issues that plague the editor today, which have been noted a million times both in these forums and on discord, but rather focus on getting mainstream features for everyone.
Ingame editors in many ways have always functioned as a sandbox for most players–an extension of the non-pvp content these games offer. A way to chill out and to look into the game more in depth other than just playing. What we got, frankly, has been a disappointment that is straight up painful to utilize meaningfully. Though it is used (painfully), it undercuts how widely utilized it could have been. And if anything, I hope that they sincerely start looking into how to properly develop it for the future, because though new DLCs and new features are great, this game needs something to sustain itself further into the future. The community has always been willing, and it is unfortunate that we simply do not have the tools.
As things stand, I imagine it would be quite grim for this community the day the last DLC is announced. I distinctively remember being excited about the editor prior to them releasing it, and they should keep their promise and deliver something proper with another cycle of production.