I don't really understand this hang up of "true raids". As far as I'm aware, there's no defined format for a "raid", just a carry over of what another specific MMO typically does for their "raids" which is ultimately just the case of two different games using the same term for different things.

There's nothing enjoyable about having to burn down trash mobs before you start a fight, especially not if you're repeating that fight over and over, which you sometimes need to do for even normal raids when you don't get the loot you need.

In fact the most boring raid in the game so far, which I loathe queuing into via the roulette, is that one Alex raid which is just a room full of trash mob spawns one after the other.
I couldn't tell you which one that is because most of the Alex raids just blur into each other as one amorphous goblin orgy. The big finishers are great, but the 1-3s are all very dull and repetitive.

Omega did it well, it had the perfect balance between some story trash you fight solo and only one time, followed by the raid bosses themselves as the actual party instances.