Is UBI unrealistic?

I’m not trying to stir the pot, but how is a universal basic income (UBI) even feasible when the state currently can’t even afford to pay pensions on its own? Pensions are funded by the taxes paid by the current workforce. Under a UBI system, there wouldn’t be wages from which to deduct pension contributions—let alone taxes to fund payments for everyone. Sure, let’s assume businesses start generating more revenue—but they’ve been doing that for the last 40 years, and it hasn’t resulted in higher tax receipts; the owners simply pocket the extra earnings. I just can’t wrap my head around how, all of a sudden, billionaires would become socially responsible and start paying massive amounts in taxes for the benefit of the world’s poorest.