Brandon unfortunately uses vB 5.0.0 as his baseline for not recommending it, the product is light years away from that today. However, vB5 lacks the modification system of the scale that vB3 and vB4 had, which is the main reason you don't see many modifications for vB5. Though some people produce them: www.vbmods.rocks.
There has also been a huge move away from people writing major modifications for free. There are people who will write custom code for you but they will charge, and rightly so.
Part of the reasoning behind this is that there was a phase when a huge number of "entitled" people started demanding instant support for free mods and posting the most awful abuse and insults when they didn't get it. It drove a lot of people away. You see this on other platforms now, a lot of stuff is paid only because of the culture of entitlement that has developed on the internet.
The other big thing I would add - the days of being able to get people to join a forum because of all your fantastic modifications are over, if they ever existed. Nobody cares if you have a classified adverts section, or can upload your own videos, or can run auctions, or play arcade games - the world has moved on, these facilities are better provided elsewhere. The remaining successful forums are about content, content, content, and also content. Nothing else.