Brainslayer is so obsessively paranoid about the idea someone might "steal" and "sell" DD-WRT devices that he obfuscates building the firmware as much as possible.
The devices also are just the stock garbage vendor GPL tarball with DD-WRT's UI on top. So you'll still be stuck with stuff like an ancient kernel full of bugs
This significantly shrinks the number of devices they support, but the devices that are supported have their lifespans increased significantly
6.x kernel is not expected to land anytime soon (late this year or early next year maybe?)
If you have a 6.x kernel, this is probably a fork of OpenWrt.
Doesn't mean everything MTK does shines under the sun, but in Linux WiFi, they are probably the most open and well supported in the modern age.