Declaring a general mobilization would mean to lose face: the master strategist admitting his perfect plan was badly botched at all levels and veering into a disaster. He's also scared of people turning against him: up to now the brunt of the conflict has been sustained by non-ethnic Russians for a reason.aka undeclared war
for some reason (?), it seems to be in everyone's interest to keep it that way
and that's why they don't cross the border
And I think it's too late for a general mobilization, he should have called it months ago, then it might have worked. But at this point mobilization is pointless: it would take months for military units to be mustered and trained, provided they can train them at all because they have sent even the training battalions to the frontline. And which equipment are they going to get? Russian material losses are staggering:
They have lost much of their 'modern' equipment and depleted their stocks of missiles and 'precision' weapons, with no results to show but an humiliating retreat. They have demonstrated an astonishing incapacity at every level of their command structure. An influx of untrained and demoralized reservists on vintage T-62 tanks is not going to help them anyway.