I doubt it would be that easy.
Discourse seems to use all the absolute worse tecnologies out there by design.
The core issue is that its badly coded Ruby. With ruby you can only expect so much performance when it comes to integrating 100 different things.
Lazy loading just needs a once over by someone competent to create some call aggregation.
Easier said than done, because the code is a bit of a mess. But being open source anyone can tinker with it (again, ask the blender folks how much time it took em) 
With regards to the PM system.
It’s not a “forum” feature. Basically it’s an email system that’s locked (tight) and can only be accessed by the forum itself.
The lack of notifications is probably due to the licensing of whatever system is in use or an issue with the specific service.
… there’s more than 1 reason why phpBB is ranked as the most used “free” forum…
All of that aside.
Performance took another turn for the worse today. I’m even having issues getting likes to trigger - slow database issues again…