I thought the Kett were such a mediocre threat. Their motivation seems to be exactly the same as the Reapers': "ascending" other species into one of them.
I thought their visual design was awesome, but story-wise, they were severely underplayed. I never respected them as a threat. I couldn't take them seriously, even less so when Liam's loyalty mission was all about mocking them as if they're nothing.
When I received message that a derelict Reaper had been found in Mass Effect 2 and that I was essentially going in to find out why a research team had gone MIA, I was like "Shit, this is going to be good!". The same happened with the Collector Ship.
I never felt this during Andromeda. Not even when finding Meridian, because the last portion of the game was so fucking rushed that I never had the time to develop the desire of FINDING Meridian, it was thrown at me five minutes later.
I really enjoyed Andromeda for its gameplay and combat, which was the best in the series, but its story is average at best. Not a good thing for a Mass Effect game.