Self nomination for quibble of the day:

Actually you could if you were referring to the main engines. Just utilize a tug which admittedly currently run on fossil fuels. There would be safety issues as more wheeled vehicles would be on runways and taxiways, but it is possible and almost undoubtedly would save some fuel.

It would still be necessary to allow the main engines to reach an optimal thermal state amd be run up prior to take off.

BTW, IIRC Southwest used to run their auxilliary power units almost continuously rather than plugging in to ground power. The theory was that this enabled faster turn around. This may no longer be the case.

To quibble further, you could use an electric tug!

To quibble a bit further still, you could use an electric tug to get the plane to the runway, then use a tow-cable to help pull the plane up to speed.  There probably hundreds of ways to play this game, and I'm sure we'll end up playing most of them.