If someone doesn't find the game fun there are two likely issues:
1. They don't really understand the game. Often this comes down to not knowing the power of quanta/research/orbitals or not understanding the value of unit composition. Can you come up with scenarios that highlight the depth of these in a way that convinces them that such aspects are more than just "oh isn't that nice" but actually crucial to gameplay depth? Show them how powerful each orbital can be when used right or how the right composition of a small force of units can defeat a much larger force.
Here, better tutorials are needed, but that is only part of the problem. The biggest way to learn how to play is to use replays, not videos. Replays allow you to slow/stop action and look around. This is one thing Planetary Annihilation did correctly, and should be used as a model on how replays should be done & offered.
Another thing missing is a "mayhem playground" mode that would be used for learning everything. That means, you have unlimited amounts of everything, and the AI should slowly at first, send a wave or two at you...getting progressively harder as time goes on. This allows people to learn how to use everything that AotS offers in their own time. In this mode, there is no game over, the AI regenerates stronger & stronger attack waves, it just continues forever until the user quits.
2. The game doesn't have what they are looking for. While some just want an iteration of their favorite RTS game, others just consider Ashes to be lacking depth. If it is indeed true that RTS games don't really begin to show off their potential until after months of post-release development, maybe the skeptical can be converted when the game reaches the more mature status. Is it viable to ask people who don't find the game fun to come back in a year?
This is a catch-all position, obviously the people that don't find this game appealing at its current incarnation are looking for something more that is missing from AotS.
The way many (most people if you look at sales vs online players) people play RTS is mainly for the single player aspect. This involves a story. This involves immersion. This makes people associate with what you are controlling and the campaign to get it done. Relic's RTS games did a good job of this most of the time for example. The next thing that can make or break a game involves game mechanics, it should make it easy to do what the user wants.
Rather than beating a dead horse about the current story & immersion of AotS (which is supposed to be in the works), people first have to get the game mechanics, and then be able to pick it up quickly.
Unfortunately, AotS makes this much harder for many people because of the many little things that need a ton of polish. Each item that has issues by itself may not mean much, but, add them all together, and it becomes a big issue.
So, is it good advice to tell people the game isn't quite finished (or "matured") yet? Well, nobody has to say anything officially, the end product shows, and lots of user reviews also tell this. There is no way to put the genie back in the bottle.
That means, to keep the current players interested, they need content to keep them from fading away.
The people that don't have this game yet are waiting for a "GOTY" edition to get a "complete" (more matured) game, though, some will buy if the game is cheap enough--but those players won't stick around that long without new content / issues fixed.