Pensions paid directly by current workers are not really so different from pensions paid out of investments. The thing that one "owns" in most of today's public equities is not physical capital (plants and equipment) but the "nexus of contracts" that allows you to make money from other peoples' labor. In other words, you are still living on backs of the working generation, same as Social Security or similar schemes.

Until we invent self-replicating physical capital (i.e. a Santa Claus machine that can make other Santa Claus machines), this will always be true.