I'm not too impressed by Reddit aoe2 anymore sadly. But I guess a lot of people enjoy it.
Part of what makes smaller subreddits good are contributors like yourself. I've seen you post a lot of informative/constructive comments. You may not always notice or realize that a lot of lurkers are soaking in the information and finding it quite useful.
The thing is with any subreddit, you will get a lot of repetition. And as a subreddit grows, naturally, you will lose the intimacy and familiarity that smaller forums can provide. And it will start being populated by people who are newer to the game, who take it more casually, who may be interested in aspects of the game that have nothing to do with the competitive side of it, and the like.
Before I became a moderator at the AoE2 subreddit, I found it quite useful and really helped me understand and learn more about the game and community. This just has to be measured because there is indeed loads of false advice, misinformation, misunderstandings about the game itself. But on average most of the time, I do think it provides a good place for people who enjoy the game to get help on things like their gaming set up, introduce them to new ideas or approaches they may not be familiar with, catch up with some games or competitive things they may not be aware of, suggest certain mods or scenarios that can enhance their fun in the game and so on and so on. And also, simply, just talk about the game we all love.
At its heart though, it's going to only be as good as members of the community like you who are kind, helpful, talented, and good at the game. And willing to share their knowledge and provide good content to engage in on the subreddit. The more people like you leave or lose interest, the more likely it is to be a place of poorer quality. Of course, nobody needs to be there or should feel any obligation.
It's just a subreddit at the end of the day.
But I don't think it will replace AoEzone or matters honestly. AoEzone is the place all us try-hards and people really deep into the community frequent. I don't see that ever disappearing (I hope not, because AoEZone has been an important part of the AoE legacy at large).
PS: On any large enough subreddit, even smaller ones like AoE2, you're able to find posts/comments to support any view you have on the nature/quality of such a forum. This is true of many other subreddits. So in truth, like many subreddits, it's just am mixed bag of things.