I paid some £500 more for the ticket than if I had flown EK or EY on the same route
And helped to keep the inefficient Air France/KLM group afloat. GBP500 is better in my pocket than someone else's. I would need a VERY good reason to spend that much more money.
If the alternative is something like Biman Bangladesh then I would understand, perhaps it's worth spending extra if it saves you on hotel accommodation with convenient arrival and departure times ie you can check in/out at normal times instead of paying for a whole night you don't use.
It may be worth sticking to a particular airline or alliance if you fly often enough to acquire and use frequent flyer miles or increase your status in the program.
Singapore Airlines and QATAR also do Jakarta one stop from Manchester.