How did they have no influence on their tax? They voted in elections on the issue and continue to do so.
Every time you vote for the status quo (even if you abstain, but enjoy the benefits anyway), then the responsibility is on you. Central government is only laying down what the electorate votes for, which includes the implicit support of policies (usually cross-party) not explicitly mentioned on manifestos.
Fact is that parties didn't want to rock the vote by saying something was unsustainable (thanks FPTP), especially against a giant bloc of regular voters who almost always decide the government and the voters who stood to benefit aren't exactly going complain about it. So while successive governments hold some responsibility for this mess, the electorate is the ultimate say in all of it.
The issue is that this particular generation is unusually large in number compared to those that came before or after and have eminence in government policy, no matter how much any further generation agitated, they'd never be able to override the voting power of such a large mostly homogeneous voting bloc. So there's not much point in campaigning (especially when it's too late to do so) for reasonable pension policy, as it's entirely in the hands of the generation that benefits from it. Helps also that the majority of the media (run by plutocrats) is more than happy to exploit the situation for other means.
No point even trying, ergo the apathy of those born after 1965.