What do we accomplish by removing sub sections? There is only one slightly inactive sub forum which is Free Graphics.
We accomplish more uniformity for sections that are not large enough to have sub-sections. Sub-sections are there to organize things. When there's not enough disorganization and content, there's no need for one. But again, my suggestion is not to remove sub-sections.
What do we gain from continuously making the site smaller and smaller?
It's not "smaller" but more compact. And we gain better navigability, as well as a higher chance for new users to enter the community. When I go to a message board and I see them have SO MANY sections on the front page in a weird, non-organized way to where I don't even know what all the forum is about, I get put off.
For example, let's say you want to look for a community where you can get help installing an FTP server from your VPS.
Would you prefer something like this?
http://www.webhostingtalk.com/
Or something like this?
https://vpsboard.com/
On the latter, you can easily see the "Tutorials and Guides" section and then you see an FTP guide in that section quickly. The user, me, has identified it quickly. However, on the more messy WebHostingTalk (granted, it is a larger message board) I have to read through all these sections. I just want to install an FTP server. So I scroll down, scroll down, keep reading. I finally see the tutorials section but it has over 10 sub-categories. So now I'm reading through the sub-categories, I finally see VPS Tutorials.
The problem with merging forums together is a lot of topics don't get noticed since there is only one forum. This is counterproductive when trying to garner activity.
A lot of topics don't get noticed? What do you mean? When more people view ONE section instead of multiple sections, ALL the threads get noticed. Sub-sections aren't there for something to get noticed. They're there for organization.
In my perspective, if I was to browse and come by this site to see it at the state you're trying to describe it, I would move on. The eye is bigger than the mind.
Please give me a scenario where a visitor would "move on" viewing my mock-up of Sythe versus the current message board.