My very first microwave - back in the late 1970's did not have a turntable. Just a large box, an unseen arm in the ceiling of the machine turned round. Loved this. Was ever so expensive then, but could put different size casserole dishes in there. It worked for nearly twenty years. Then my youngest son slammed the door so hard, the glass broke. Due to its age was not possible to repair, got paid out on household insurance, but could not find anything similar then in the shops. I asked Philips why they did not make these anymore, only the ones with the turntables, and was told that the public did not trust m.waves if they could net see the food turning around. Sounds like they are now back.
However, I would, like other here, unless you are usually cooking for a large family, then the small, cheap ones with limited functions are the best. Best use for microwave is just that, - porridge, baked potatoes, heating milk, water, scrambled//poached eggs, baked beans, etc.