The power needed to drive a large fan is currently beyond of what is technically possible in gearbox engineering. The swirl losses of a single-stage fan can be somewhat recouped by inclining the struts holding the fan fairing, so a contra-rotating fan is not much of a help, but a tremendous engineering challenge.
EDIT: Clarification: Small geared fans do exist for a few decades already (Lycoming ALF502) and the maximum size of geared fans is increasing, but the size of the biggest engines is still far out of reach of today's technical possibilities. The biggest geared fan today has ⅓ of the thrust of large turbofans.
