In my opinion, as a large server owner, quality is often reflected by the size of your server (if you are going for size). This might not be a popular opinion, but in my opinion the idea that all these little servers have superior content or more dedicated staff and are only small because of the way advertisements work, while it obviously has some merit, has a lot less effect that is generally assumed in the long term.
As someone with a lot of experience with growth attraction, there are a few metrics you shoot for. One of them is certainly exposure, through voting sites, pmc, minecraftforums, youtube, etc. But as important, or more important in creating a server that maintains a sizable and stable population is the quality of the server.
If every server took a turn on the front page for a day and got 1000 view in that time, you would see a very large difference in the amount of growth each server actually attracted and maintained.
When your server is high quality, stable, runs smoothly and has something unique to offer players, you something called high retention. Retention is the most important element of server growth. This is manifested in the amount of players who log into your server who actually stay, (so that if you have high retention, you might keep 50/100 players vs. a server with a lot of exposure but low retention, might keep 25/300 players) and, something that gets ignored a lot, the amount of players on your server who invite their friends. This second metric is extremely important and is a huge part of building a stable and cohesive playerbase, and it is completely independent of the portrayed prevalence of server advertisement sites.
The point of this being, quality servers, if they are active in their advertisements, regardless of the exact method that the sites they advertise use, generally will grow, and will then become large servers themselves, attaining high exposure on those sites biased to large servers, and thus be rewarded for their quality and encourage high quality servers.
This way low quality servers do not get a disproportionate amount of attention, because of the difficulty of breaking into that realm of larger servers.
P.S. In a merit based system, parameters like length of update logs and server specs really should already be rolled into the size/reviews of the server and do not need a separate parameter, that would just immediately be bypassed by people writing long tutorials and spam in their update logs and people lying about their server specs (Spoken as someone who details just about every change I do in every patch, and who has very good specs on their server)
