@Bri It's a constant battle to not alienate plugin developers with changes to core. For the most part our changes have been minimal, at least within the past couple of months, though there was definitely a period where breaking changes were in almost every single version.
We've wanted to re-instate the plugin contests for awhile now, although we've been quite busy with other work related to NodeBB as well 
However, since 1.5.0 was launched, we're a little more free and a burden has been lifted off of us as we're no longer in a constant mode of keeping the prerelease branch up-to-date with the latest changes from master.
My main concern over the past couple of minor versions was to build a system that was tolerant to plugins becoming out of date. The nbbpm.compatibility system is definitely reducing the issues we're seeing with outdated plugins, but at the cost of many more plugins marked out-of-date (and thus not showing up in NodeBB out of the box).
It's an unfortunate trade-off, but I am not entirely sure what my next step would be here...