Hell, for less than 10k MAU you can still get away with shared hosting if you're really strapped for cash, 5-7 bucks per month.
People around here really lost perspective of what can be accomplished with a dedicated box and a PHP forum.
You don't need kubernetes to handle 12 AWS instances in 3 regions, with S3 storage and distributed RDS with a side dish of lambdas to run your 45 microservices.
It's relatively harder to make your forum even known among potential interested users on the background of the entire Web, while you have a much narrower search space within reddit.com. (Widely popular Facebook groups also exist.)
I'm in a carseat facebook group, and people constantly post engagement spam, I'm really not sure to what end, but I assume it somehow makes other facebook posts visible. Then there's the run of the mill scams that hit all kinds of networks.
"My Autistic Son loves 'Yamaha Boat Outboard Motors' and made these T-Shirt. Please take a look and let him know what you think, he loves comments~~~"
Then I get tons of youtube videos for topics that have all the keywords I need but are literally not even working on the same vehicle or problem I'm looking for, but of course you can't figure that out until 3 or 4 minutes into the video.
The few dedicated sites I'm still in that are active are far and away better than their reddit /facebook/ instagram /discord contemporaries. Though have still declined from the 2000s.
At least you can search reddit with google. Facebook you can't find anything, sometimes I can't even find the groups that I'm a member of.