In the past I would have recommended Tracktion from Mackie. But they basically have abandoned the code leaving users in the dust. My Tracktion 2 is a stability workhorse and for me, it's visual oriented track representation and signal flow for both MIDI and Audio fit my mental paradigm like hand-in-glove.

I too have tried Live - but it really is aimed at loop and pattern based on/off composition.

I have a very old version of Magix - didn't like that it was 2 separated applications for audio and midi tracks at the time.

PTPA was fairly simple, but began to lag behind the times for plugin support; slowly crawling back to usability.

Without a clear definition of where simplicity is lacking it's quite difficult to provide any further direction.

I got very tired of the multi-window stackup that can occur with nearly all DAW programs. That's what really attracted me to Tracktion. Some Apple users speak of similar one-screen simplicity with Garageband and it's big-brother, Logic. The last version of Tracktion actually stepped away somewhat from the simple and the added complexity tanked it so it seems.

Good thing the Tracktion 2 is still cranking away. One thing I miss with it is that it has no notation editing for midi - something which PTPA actually excels with.