Bless you all for your willingness & passion!
Wikis frequently get blamed for their ability to demonstrate the second law of thermodynamics: Entropy. With over a decade of contributions, out documentation is full of crust. It would undoubtedly benefit from a good Spring cleaning.
I agree with your sentiments of trying to focus efforts. That’s why, for example, I shamelessly direct new devs to om.rs/gettingstarted and keep promoting om.rs/devmanual as a dev reference and to om.rs/guide for an implementer guide along with the wiki. It’s not because I think these are the perfect resources; rather, we’re better of trying to get everyone looking at the same artifacts and iterate on improving them instead of continually making new artifacts that end up getting outdated and adding to the problem.
So, here’s a big cheers to anyone willing to roll up their sleeves and improve what we’ve got instead of making the next new thing! 
It’s worth noting that our latest platform release is made for Java 8 and does not support later versions. The next platform release (Platform 2.4) will support Java 8, 11, 13, and 14 (most importantly Java 8, which is in most production environments, and Java 11, as our goal is to support LTS versions).
The recently released Reference Application 2.10 uses Platform 2.3, so will need Java 8 and will undoubtedly require old versions of Tomcat & MySQL.
Personally, I’d like to see us migrating toward production support of containers (e.g., a Docker stack), which avoids the OS-specific variations and gives us more flexibility & predictability with deployment. Let those with the time & expertise play with custom installs of J2EE containers, databases, etc.
But this will take some time. For now, some clear direction on how to quickly get a system up & running in the wiki & community reference manuals would be most welcome.