The “stuff” is like scenery, airport, liveries and other 3rd party apps that our awesome community did but coming from personal users/beginners developers if you like to put it at. I have all those stuff in my community folder and after I removed them all and just use the one that coming from a reliable source like FlyByWire, Project Mega Pack, FSUIPC to name a few meaning from all this people who are active in updating their products. I keep those. The one that haven’t being updated since the released of other patches up to the recent one. I save it in my other folder just incase the owner come back and updated them accordingly.
and to your second question, why its effect our community folder right? it doesn’t make any sense at all but I saw this one announcement from Asobo in 1.14.5.0 release nots
"RELEASE NOTES 1.14.5.0
Some packages in your community folder may not have been updated and, as a result, may have an unexpected impact on the title’s performance and behaviour."
I tried this an to my amazement, the sim performs way much better! So, from that day I will be selective in what I put in that community folder.
this is some ground picture, you may need to download the pic and open it using app in your PC then just click from this post to be able to see the nice crisp pic.
but, I feel very happy but Asobo there is still more room of improvement that you need to fix like B787 still acting like a dolphin on the runaway for example. Still not fix yet 
anyway, i have a flight to catch! later 