Someone answered you and told you it was the 'next legal challenge' however it will be doomed to failure as both schemes are totally different people seem to think that if you reached pension age before 2016 you only get the old basic and if you reached pension age after 2016 you automatically get the higher amount neither is actually true, people reaching pension age pre 2016 had the opportunity to pay into the second state pensions, graduated retirement and SERPS which were earnings related and S2P which had a lower earning threshold and included any NI credits given with some benefits, SERPS alone under the the new rate could give people up to £204.68 a week in addition to their basic pensions, I don't know anyone who gets that amount but my two older sisters and my husband who are on the old scheme get way above the old basic and actually a lot more than the new full pension due to SERPS, yes not everyone could pay into the second state pensions but the OPPORUNITY was there.
This opportunity has been denied to younger pensioners since 2016, some including myself due to the transition rules get a protected payment that made up for the SERPS we would have got under the the old scheme so get more than the full pension so in actual fact a lot of younger pensioners will lose out especially those with little or no NI history pre 2016, my son will never get the same state pension as my husband and myself, even though his earnings would have been enough for him to be automatically enrolled into the SSPS if the rules had not changed, there is unfairness on bith sides.