Narrow your niche and lock your members in.
That's the advice I would give for this year (and probably the next few years).
There isn't enough time and attention to go round. The number of people is relatively finite and the number of communities growing rapidly.
Many communities are about to be squeezed out of existence. The era of exponential growth is over. The number of active members in most communities is going to pleateau and then, in many cases, begin to decline. Whether that is a permanent decline remains to be seen.
This makes it important to first narrow your niche to one that more strongly matches the interest of a smaller segment of your target audience. If necessary develop multiple communities for multiple segments. Then, second, build a strong sense of community to lock members into that community.
A sense of community is a future-proof approach. Members don't leave when a new platform arrive, instead you can move your community from one platform to the next – or keep them where they are. There are many smaller, highly focused, communities that have been around for over a decade using older technology.
To summarize, narrow your focus and lock them in. This is almost certainly the most important thing you can do right now.