I rode with Turkish airlines about 10 years ago from Jakarta to Istanbul. The cabin crew were the unhappiest bunch I've ever encountered on any airline, ever.
One steward was constantly seething with anger, he must have stewing over some mistreatment. The service was desultory, and the food was nothing to write home about.
The Turkish Airlines aircraft are in pretty good shape and reasonably new, and they have a very large fleet.
Sabiha Gocken airport is extremely modern and clean, and the Turks are quite efficient. Probably the saddest sight I've seen though, was a fully sealed smoking room in the airport, where flight and cabin crew from countries where smoking was still very prevalent, could puff away to their hearts content, and fill themselves up with nicotine before they made the dash to their destination. The room looked like it was on fire.
I recall seeing one Russian Captain puffing away desperately in the room, he looked like a walking heart attack, red-faced and bloated. I would have been very reluctant to fly if I knew he was up front.
We left Sabiha Gocken on an EgyptAir flight to Cairo. Now THAT was a hairy ride! Passengers ignoring seatbelt signs, walking around and swapping seats at all stages of the flight.
The flight was 3 hrs late taking off, and when we did finally take off, I swear the Captain had the throttles firewalled from the start of the runway, to the start of the descent into Cairo.
And Cairo Airport cannot be adequately described. Security was virtually non-existent, and there was a VIP lounge on the upper level, that was open to the air! - and open to all the flies!