I've had a bike stolen with a cable lock on, never again!
Yes they can cut through a good D lock but theres not many opportunits around with an angle grinder who would use it in broad daylight when the bike is parked in a public space for a very short time, with a lot of people passing by.
If you leave a bike where its not going to be seen like the OP did then anyone can work on it without a care in the world.
Its about making it more difficult, they have got to have the tools, have the time to do it and be able to find it.
This
I got fed up with storing the bikes in the house, so I had an Agard fitted in the garden, £600 very well spent...and it takes 4 full size bikes
I pretty much only use a D Lock away from home if leaving the bike. I'm no lightweight so frankly adding 2kg of Abus to my rack bag makes diddly difference, preferred to putting on the frame
My new work place has secure bike area (hopefully), I've left my spare D lock there, even though I'll probably ride a day a week max, as I also have to carry a heavy old laptop, shoes, clothes etc