“It's a shame that pension credits can't be phased out and the new pension be improved…”
The problem is, f-f, that the State Pension Scheme is inextricably linked with retirement age benefits. All people of pensionable age are guaranteed a minimum income regardless of their contributions to the pot. This leads to such situations as I described above. If the State wants to provide people with a minimum income (whether in “retirement” or whilst of working age) that is one question. The muddle with the State Pension is that the payments made to those who have made the required contributions are conflated with those made to people who have not. Thus the State Pension scheme (which includes both types of recipients) is seen as unsustainable. In fact the State Pension scheme, when the beneficiaries are considered to be solely those who have made the required contributions (or who receive reduced payments because they have not) and whose pensions are calculated on that basis is entirely sustainable. It is only when the payments which do not relate to contributions – including Pension Credits – are included that the scheme becomes burdensome.
In addition to that the new (so-called) flat-rate pension is extremely unfair on those who were already in receipt of their pension when it was introduced. You can see that the difference in the rates amounts to around £2,000 a year. This means that over an average pension period of around 20 years an older recipient (perhaps older by just one day and who may have made up to 40 years of NI contributions) is around £40k worse off than the younger (who needs to have made only 35 years contributions). The system, despite its simplification, is grossly unfair towards those who have contributed the most. But that's the way things are in many respects in the UK.