I LOVE the Genos, and Tyros line before them.. The first arranger I used was Band-in-a-box, almost 30 years ago. I quit playing in bands, and working in studios when I was 30. I enjoy playing all the parts. Before arrangers it was a much more laborious process. You had to 'build' the song to a certain stage, to really feel 'where it was going to go. I never used any arranger, as the whole entity of the song. (Granted the Tyros and Genos are great playing live, in one take)..
What I loved about Band-in-a-box was that it would give you a quick sound picture of what the song was going to sound like. Previous to that, it would take me a few hours to build the song, then realize I wanted to change the chords, the key, change tempo, etc. Then have to start from scratch again. With Genos you can very quickly create a song. Listen, and redo to make any changes you want.
I sometimes use the style created parts as is. Quite often I use it as the starting idea and build from there.
I think each persons approach is individual. If I was a brilliant piano player (which I am not).. I would likely be more inclined to play solo piano. The beauty of an arranger kbd is, you can use it to varying degrees. If you joy and fun, playing live. it's perfect for that. If you want to create the 'bed' of the song, and play your own melody, or overdub additional line onto the song.
It is extremely satisfying to play a keyboard and have it create a rich full sound. It's up to each person's technique and use, how effective an arranger kbd is to them.