I think MLOK makes sense because they’re not true MLOK. They’re MLOK with a picatinny rail across the top. From a weight / ergonomics perspective it’s great.
I have an old VTAC rail on a BCM mid length. If you squint real hard - you’ll realize it’s almost the same thing rail with slot mounts (that are different from MLOK, but visually basically the same) and a picatinny rail across the top.
It just makes sense and has for a long time. Unless you want your light somewhere else on the gun.
Now, where it fails is it attaches to a traditional barrel nut and doesn’t give a lot of repeatability for POI/POA or rigidity for IR.
But, I shoot steel cased ammo, within 100 yards almost exclusively, and only have a WML on one gun. So it’s diminishing returns and thus I haven’t gone to rails on all my guns. At this point - I’d just buy a factory AR with the rail I liked or as close to it as possible.
Lots of great info in this thread.